Basic Geometry : 45/45/90 Right Isosceles Triangles

Study concepts, example questions & explanations for Basic Geometry

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Example Questions

Example Question #2 : How To Find The Length Of The Side Of A 45/45/90 Right Isosceles Triangle

If the hypotenuse of a right isosceles triangle is \displaystyle \sqrt6, what is the length of a side of the triangle?

Possible Answers:

\displaystyle \sqrt3

\displaystyle 2\sqrt3

\displaystyle 12

\displaystyle 16

Correct answer:

\displaystyle \sqrt3

Explanation:

A right isosceles triangle is also a \displaystyle 45-45-90 triangle.

13

To find the length of a side, we will need to use the Pythagorean Theorem:

\displaystyle a^2+b^2=c^2

Since this is an isosceles triangle, 

\displaystyle a=b

The Pythagorean Theorem can then be rewritten as the following:

\displaystyle a^2+a^2=c^2

\displaystyle 2a^2=c^2

Since we are trying to find the length of a side of this triangle, solve for \displaystyle a.

\displaystyle a^2=\frac{c^2}{2}

Simplify.

\displaystyle a=\sqrt{\frac{c^2}{2}}

\displaystyle a=\frac{c}{\sqrt2}

Multiply the fraction by one in the form of \displaystyle \frac{\sqrt{2}}{\sqrt{2}}.

\displaystyle a=\frac{c}{\sqrt2}\times\frac{\sqrt{2}}{\sqrt{2}}

Solve.

\displaystyle a=\frac{c\sqrt2}{2}

Now, substitute in the length of the hypotenuse in for \displaystyle c to solve for the side of the triangle in the question.

\displaystyle a=\frac{(\sqrt6)(\sqrt2)}{2}

Simplify.

\displaystyle a=\frac{\sqrt{12}}{2}

Reduce.

\displaystyle a=\sqrt3

Example Question #7 : How To Find The Length Of The Side Of A 45/45/90 Right Isosceles Triangle

If the hypotenuse of a right isosceles triangle is \displaystyle 2\sqrt2, what is the length of a side of this triangle?

Possible Answers:

\displaystyle 2

\displaystyle \sqrt3

\displaystyle 4

\displaystyle \sqrt2

Correct answer:

\displaystyle 2

Explanation:

A right isosceles triangle is also a \displaystyle 45-45-90 triangle.

13

To find the length of a side, we will need to use the Pythagorean Theorem:

\displaystyle a^2+b^2=c^2

Since this is an isosceles triangle, 

\displaystyle a=b

The Pythagorean Theorem can then be rewritten as the following:

\displaystyle a^2+a^2=c^2

\displaystyle 2a^2=c^2

Since we are trying to find the length of a side of this triangle, solve for \displaystyle a.

\displaystyle a^2=\frac{c^2}{2}

Simplify.

\displaystyle a=\sqrt{\frac{c^2}{2}}

\displaystyle a=\frac{c}{\sqrt2}

Multiply the fraction by one in the form of \displaystyle \frac{\sqrt{2}}{\sqrt{2}}.

\displaystyle a=\frac{c}{\sqrt2}\times\frac{\sqrt{2}}{\sqrt{2}}

Solve.

\displaystyle a=\frac{c\sqrt2}{2}

Now, substitute in the length of the hypotenuse in for \displaystyle c to solve for the side of the triangle in the question.

\displaystyle a=\frac{(2\sqrt2)(\sqrt2)}{2}

Simplify.

\displaystyle a=\frac{\sqrt{4}}{2}

Reduce.

\displaystyle a=2

Example Question #4 : How To Find The Length Of The Side Of A 45/45/90 Right Isosceles Triangle

If the hypotenuse of a right isosceles triangle is \displaystyle \sqrt{10}, what is the length of a side of this triangle?

Possible Answers:

\displaystyle \sqrt5

\displaystyle 2

\displaystyle \sqrt3

\displaystyle \sqrt6

Correct answer:

\displaystyle \sqrt5

Explanation:

A right isosceles triangle is also a \displaystyle 45-45-90 triangle.

13

To find the length of a side, we will need to use the Pythagorean Theorem:

\displaystyle a^2+b^2=c^2

Since this is an isosceles triangle, 

\displaystyle a=b

The Pythagorean Theorem can then be rewritten as the following:

\displaystyle a^2+a^2=c^2

\displaystyle 2a^2=c^2

Since we are trying to find the length of a side of this triangle, solve for \displaystyle a.

\displaystyle a^2=\frac{c^2}{2}

Simplify.

\displaystyle a=\sqrt{\frac{c^2}{2}}

\displaystyle a=\frac{c}{\sqrt2}

Multiply the fraction by one in the form of \displaystyle \frac{\sqrt{2}}{\sqrt{2}}.

\displaystyle a=\frac{c}{\sqrt2}\times\frac{\sqrt{2}}{\sqrt{2}}

Solve.

\displaystyle a=\frac{c\sqrt2}{2}

Now, substitute in the length of the hypotenuse in for \displaystyle c to solve for the side of the triangle in the question.

\displaystyle a=\frac{(\sqrt{10})(\sqrt2)}{2}

Simplify.

\displaystyle a=\frac{\sqrt{20}}{2}

Reduce.

\displaystyle a=\sqrt5

Example Question #171 : Triangles

If the hypotenuse of a right isosceles triangle is \displaystyle \sqrt{14}, what is the length of a side of the triangle?

Possible Answers:

\displaystyle \sqrt7

\displaystyle 2\sqrt2

\displaystyle 2\sqrt{7}

\displaystyle \sqrt{15}

Correct answer:

\displaystyle \sqrt7

Explanation:

A right isosceles triangle is also a \displaystyle 45-45-90 triangle.

13

To find the length of a side, we will need to use the Pythagorean Theorem:

\displaystyle a^2+b^2=c^2

Since this is an isosceles triangle, 

\displaystyle a=b

The Pythagorean Theorem can then be rewritten as the following:

\displaystyle a^2+a^2=c^2

\displaystyle 2a^2=c^2

Since we are trying to find the length of a side of this triangle, solve for \displaystyle a.

\displaystyle a^2=\frac{c^2}{2}

Simplify.

\displaystyle a=\sqrt{\frac{c^2}{2}}

\displaystyle a=\frac{c}{\sqrt2}

Multiply the fraction by one in the form of \displaystyle \frac{\sqrt{2}}{\sqrt{2}}.

\displaystyle a=\frac{c}{\sqrt2}\times\frac{\sqrt{2}}{\sqrt{2}}

Solve.

\displaystyle a=\frac{c\sqrt2}{2}

Now, substitute in the length of the hypotenuse in for \displaystyle c to solve for the side of the triangle in the question.

\displaystyle a=\frac{(\sqrt{14})(\sqrt2)}{2}

Simplify.

\displaystyle a=\frac{\sqrt{28}}{2}

Reduce.

\displaystyle a=\sqrt7

Example Question #172 : Triangles

If the hypotenuse of a right isosceles triangle is \displaystyle 12\sqrt2, what is the length of a side of the triangle?

Possible Answers:

\displaystyle 18

\displaystyle 6

\displaystyle 12

\displaystyle 24

Correct answer:

\displaystyle 12

Explanation:

A right isosceles triangle is also a \displaystyle 45-45-90 triangle.

13

To find the length of a side, we will need to use the Pythagorean Theorem:

\displaystyle a^2+b^2=c^2

Since this is an isosceles triangle, 

\displaystyle a=b

The Pythagorean Theorem can then be rewritten as the following:

\displaystyle a^2+a^2=c^2

\displaystyle 2a^2=c^2

Since we are trying to find the length of a side of this triangle, solve for \displaystyle a.

\displaystyle a^2=\frac{c^2}{2}

Simplify.

\displaystyle a=\sqrt{\frac{c^2}{2}}

\displaystyle a=\frac{c}{\sqrt2}

Multiply the fraction by one in the form of \displaystyle \frac{\sqrt{2}}{\sqrt{2}}.

\displaystyle a=\frac{c}{\sqrt2}\times\frac{\sqrt{2}}{\sqrt{2}}

Solve.

\displaystyle a=\frac{c\sqrt2}{2}

Now, substitute in the length of the hypotenuse in for \displaystyle c to solve for the side of the triangle in the question.

\displaystyle a=\frac{(12\sqrt2)(\sqrt2)}{2}

Simplify.

\displaystyle a=\frac{24}{2}

Reduce.

\displaystyle a=12

Example Question #173 : Triangles

If the hypotenuse of a right isosceles triangle is \displaystyle 2\sqrt5, what is the length of a side of the triangle?

Possible Answers:

\displaystyle 3

\displaystyle 4\sqrt2

\displaystyle \sqrt{10}

\displaystyle 2\sqrt3

Correct answer:

\displaystyle \sqrt{10}

Explanation:

A right isosceles triangle is also a \displaystyle 45-45-90 triangle.

13

To find the length of a side, we will need to use the Pythagorean Theorem:

\displaystyle a^2+b^2=c^2

Since this is an isosceles triangle, 

\displaystyle a=b

The Pythagorean Theorem can then be rewritten as the following:

\displaystyle a^2+a^2=c^2

\displaystyle 2a^2=c^2

Since we are trying to find the length of a side of this triangle, solve for \displaystyle a.

\displaystyle a^2=\frac{c^2}{2}

Simplify.

\displaystyle a=\sqrt{\frac{c^2}{2}}

\displaystyle a=\frac{c}{\sqrt2}

Multiply the fraction by one in the form of \displaystyle \frac{\sqrt{2}}{\sqrt{2}}.

\displaystyle a=\frac{c}{\sqrt2}\times\frac{\sqrt{2}}{\sqrt{2}}

Solve.

\displaystyle a=\frac{c\sqrt2}{2}

Now, substitute in the length of the hypotenuse in for \displaystyle c to solve for the side of the triangle in the question.

\displaystyle a=\frac{(2\sqrt5)(\sqrt2)}{2}

Simplify.

\displaystyle a=\frac{2\sqrt{10}}{2}

Reduce.

\displaystyle a=\sqrt{10}

Example Question #11 : How To Find The Length Of The Side Of A 45/45/90 Right Isosceles Triangle

If the hypotenuse of a right isosceles triangle is \displaystyle 12\sqrt{7}, what is the length of one side of the triangle?

Possible Answers:

\displaystyle 8\sqrt{10}

\displaystyle 3\sqrt{22}

\displaystyle 12

\displaystyle 6\sqrt{14}

Correct answer:

\displaystyle 6\sqrt{14}

Explanation:

A right isosceles triangle is also a \displaystyle 45-45-90 triangle.

13

To find the length of a side, we will need to use the Pythagorean Theorem:

\displaystyle a^2+b^2=c^2

Since this is an isosceles triangle, 

\displaystyle a=b

The Pythagorean Theorem can then be rewritten as the following:

\displaystyle a^2+a^2=c^2

\displaystyle 2a^2=c^2

Since we are trying to find the length of a side of this triangle, solve for \displaystyle a.

\displaystyle a^2=\frac{c^2}{2}

Simplify.

\displaystyle a=\sqrt{\frac{c^2}{2}}

\displaystyle a=\frac{c}{\sqrt2}

Multiply the fraction by one in the form of \displaystyle \frac{\sqrt{2}}{\sqrt{2}}.

\displaystyle a=\frac{c}{\sqrt2}\times\frac{\sqrt{2}}{\sqrt{2}}

Solve.

\displaystyle a=\frac{c\sqrt2}{2}

Now, substitute in the length of the hypotenuse in for \displaystyle c to solve for the side of the triangle in the question.

\displaystyle a=\frac{(12\sqrt7)(\sqrt2)}{2}

Simplify.

\displaystyle a=\frac{12\sqrt{14}}{2}

Reduce.

\displaystyle a=6\sqrt{14}

Example Question #175 : Triangles

If the hypotenuse of a right isosceles triangle is \displaystyle 4\sqrt{3}, what is the length of one side of the triangle?

Possible Answers:

\displaystyle 2\sqrt6

\displaystyle 8\sqrt3

\displaystyle 6\sqrt2

\displaystyle 4\sqrt6

Correct answer:

\displaystyle 2\sqrt6

Explanation:

A right isosceles triangle is also a \displaystyle 45-45-90 triangle.

13

To find the length of a side, we will need to use the Pythagorean Theorem:

\displaystyle a^2+b^2=c^2

Since this is an isosceles triangle, 

\displaystyle a=b

The Pythagorean Theorem can then be rewritten as the following:

\displaystyle a^2+a^2=c^2

\displaystyle 2a^2=c^2

Since we are trying to find the length of a side of this triangle, solve for \displaystyle a.

\displaystyle a^2=\frac{c^2}{2}

Simplify.

\displaystyle a=\sqrt{\frac{c^2}{2}}

\displaystyle a=\frac{c}{\sqrt2}

Multiply the fraction by one in the form of \displaystyle \frac{\sqrt{2}}{\sqrt{2}}.

\displaystyle a=\frac{c}{\sqrt2}\times\frac{\sqrt{2}}{\sqrt{2}}

Solve.

\displaystyle a=\frac{c\sqrt2}{2}

Now, substitute in the length of the hypotenuse in for \displaystyle c to solve for the side of the triangle in the question.

\displaystyle a=\frac{(4\sqrt3)(\sqrt2)}{2}

Simplify.

\displaystyle a=\frac{4\sqrt{6}}{2}

Reduce.

\displaystyle a=2\sqrt6

Example Question #176 : Triangles

If the hypotenuse of a right isosceles triangle is \displaystyle 9\sqrt6, what is the length of one side of the triangle?

Possible Answers:

\displaystyle 9\sqrt2

\displaystyle 9\sqrt3

\displaystyle \frac{9\sqrt2}{2}

\displaystyle \frac{9\sqrt3}{2}

Correct answer:

\displaystyle 9\sqrt3

Explanation:

A right isosceles triangle is also a \displaystyle 45-45-90 triangle.

13

To find the length of a side, we will need to use the Pythagorean Theorem:

\displaystyle a^2+b^2=c^2

Since this is an isosceles triangle, 

\displaystyle a=b

The Pythagorean Theorem can then be rewritten as the following:

\displaystyle a^2+a^2=c^2

\displaystyle 2a^2=c^2

Since we are trying to find the length of a side of this triangle, solve for \displaystyle a.

\displaystyle a^2=\frac{c^2}{2}

Simplify.

\displaystyle a=\sqrt{\frac{c^2}{2}}

\displaystyle a=\frac{c}{\sqrt2}

Multiply the fraction by one in the form of \displaystyle \frac{\sqrt{2}}{\sqrt{2}}.

\displaystyle a=\frac{c}{\sqrt2}\times\frac{\sqrt{2}}{\sqrt{2}}

Solve.

\displaystyle a=\frac{c\sqrt2}{2}

Now, substitute in the length of the hypotenuse in for \displaystyle c to solve for the side of the triangle in the question.

\displaystyle a=\frac{(9\sqrt6)(\sqrt2)}{2}

Simplify.

\displaystyle a=\frac{9\sqrt{12}}{2}

\displaystyle a=\frac{18\sqrt3}{2}

Reduce.

\displaystyle a=9\sqrt3

Example Question #177 : Triangles

If the hypotenuse of a right isosceles triangle is \displaystyle 128, what is the length of a side of the triangle?

Possible Answers:

\displaystyle 64

\displaystyle 64\sqrt2

\displaystyle 128

\displaystyle 32\sqrt3

Correct answer:

\displaystyle 64\sqrt2

Explanation:

A right isosceles triangle is also a \displaystyle 45-45-90 triangle.

13

To find the length of a side, we will need to use the Pythagorean Theorem:

\displaystyle a^2+b^2=c^2

Since this is an isosceles triangle, 

\displaystyle a=b

The Pythagorean Theorem can then be rewritten as the following:

\displaystyle a^2+a^2=c^2

\displaystyle 2a^2=c^2

Since we are trying to find the length of a side of this triangle, solve for \displaystyle a.

\displaystyle a^2=\frac{c^2}{2}

Simplify.

\displaystyle a=\sqrt{\frac{c^2}{2}}

\displaystyle a=\frac{c}{\sqrt2}

Multiply the fraction by one in the form of \displaystyle \frac{\sqrt{2}}{\sqrt{2}}.

\displaystyle a=\frac{c}{\sqrt2}\times\frac{\sqrt{2}}{\sqrt{2}}

Solve.

\displaystyle a=\frac{c\sqrt2}{2}

Now, substitute in the length of the hypotenuse in for \displaystyle c to solve for the side of the triangle in the question.

\displaystyle a=\frac{128(\sqrt2)}{2}

Simplify.

\displaystyle a=64\sqrt2

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