Basic Geometry : Quadrilaterals

Study concepts, example questions & explanations for Basic Geometry

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Example Questions

Example Question #102 : Squares

Find the area of a square if it has a diagonal of \(\displaystyle \sqrt5\).

Possible Answers:

\(\displaystyle 5\)

\(\displaystyle 5\sqrt2\)

\(\displaystyle \frac{5}{2}\)

\(\displaystyle \frac{15}{2}\)

Correct answer:

\(\displaystyle \frac{5}{2}\)

Explanation:

The diagonal of a square is also the hypotenuse of a \(\displaystyle 45-45-90\) triangle.

Picture1

Recall how to find the area of a square:

\(\displaystyle \text{Area}=\text{side}^2\)

Now, use the Pythagorean theorem to find the area of the square.

\(\displaystyle \text{side}^2+\text{side}^2=\text{Diagonal}^2\)

\(\displaystyle 2(\text{side})^2=\text{Diagonal}^2\)

\(\displaystyle \text{side}^2=\frac{\text{Diagonal}^2}{2}\)

\(\displaystyle \text{Area}=\text{side}^2=\frac{\text{Diagonal}^2}{2}\)

Substitute in the length of the diagonal to find the area of the square.

\(\displaystyle \text{Area}=\frac{(\sqrt5)^2}{2}\)

Simplify.

\(\displaystyle \text{Area}=\frac{5}{2}\)

Example Question #103 : Squares

Find the area of a square if it has a diagonal of \(\displaystyle \sqrt3\).

Possible Answers:

\(\displaystyle \frac{3\sqrt2}{2}\)

\(\displaystyle 3\sqrt2\)

\(\displaystyle \frac{3}{2}\)

\(\displaystyle \sqrt3\)

Correct answer:

\(\displaystyle \frac{3}{2}\)

Explanation:

The diagonal of a square is also the hypotenuse of a \(\displaystyle 45-45-90\) triangle.

Picture1

Recall how to find the area of a square:

\(\displaystyle \text{Area}=\text{side}^2\)

Now, use the Pythagorean theorem to find the area of the square.

\(\displaystyle \text{side}^2+\text{side}^2=\text{Diagonal}^2\)

\(\displaystyle 2(\text{side})^2=\text{Diagonal}^2\)

\(\displaystyle \text{side}^2=\frac{\text{Diagonal}^2}{2}\)

\(\displaystyle \text{Area}=\text{side}^2=\frac{\text{Diagonal}^2}{2}\)

Substitute in the length of the diagonal to find the area of the square.

\(\displaystyle \text{Area}=\frac{(\sqrt3)^2}{2}\)

Simplify.

\(\displaystyle \text{Area}=\frac{3}{2}\)

Example Question #104 : Squares

Find the area of a square if it has a diagonal of \(\displaystyle \sqrt6\).

Possible Answers:

\(\displaystyle \sqrt6\)

\(\displaystyle 6\sqrt2\)

\(\displaystyle 3\sqrt2\)

\(\displaystyle 3\)

Correct answer:

\(\displaystyle 3\)

Explanation:

The diagonal of a square is also the hypotenuse of a \(\displaystyle 45-45-90\) triangle.

Picture1

Recall how to find the area of a square:

\(\displaystyle \text{Area}=\text{side}^2\)

Now, use the Pythagorean theorem to find the area of the square.

\(\displaystyle \text{side}^2+\text{side}^2=\text{Diagonal}^2\)

\(\displaystyle 2(\text{side})^2=\text{Diagonal}^2\)

\(\displaystyle \text{side}^2=\frac{\text{Diagonal}^2}{2}\)

\(\displaystyle \text{Area}=\text{side}^2=\frac{\text{Diagonal}^2}{2}\)

Substitute in the length of the diagonal to find the area of the square.

\(\displaystyle \text{Area}=\frac{(\sqrt6)^2}{2}\)

Simplify.

\(\displaystyle \text{Area}=\frac{6}{2}\)

\(\displaystyle \text{Area}=3\)

 

Example Question #105 : Squares

Find the area of a square if it has a diagonal of \(\displaystyle \sqrt{10}\).

Possible Answers:

\(\displaystyle 15\)

\(\displaystyle 10\)

\(\displaystyle 5\sqrt2\)

\(\displaystyle 5\)

Correct answer:

\(\displaystyle 5\)

Explanation:

The diagonal of a square is also the hypotenuse of a \(\displaystyle 45-45-90\) triangle.

Picture1

Recall how to find the area of a square:

\(\displaystyle \text{Area}=\text{side}^2\)

Now, use the Pythagorean theorem to find the area of the square.

\(\displaystyle \text{side}^2+\text{side}^2=\text{Diagonal}^2\)

\(\displaystyle 2(\text{side})^2=\text{Diagonal}^2\)

\(\displaystyle \text{side}^2=\frac{\text{Diagonal}^2}{2}\)

\(\displaystyle \text{Area}=\text{side}^2=\frac{\text{Diagonal}^2}{2}\)

Substitute in the length of the diagonal to find the area of the square.

\(\displaystyle \text{Area}=\frac{(\sqrt{10})^2}{2}\)

Simplify.

\(\displaystyle \text{Area}=\frac{10}{2}\)

\(\displaystyle \text{Area}=5\)

Example Question #106 : Squares

Find the area of a square if it has a diagonal of \(\displaystyle 4\sqrt3\).

Possible Answers:

\(\displaystyle 18\sqrt2\)

\(\displaystyle 18\)

\(\displaystyle 4\sqrt6\)

\(\displaystyle 24\)

Correct answer:

\(\displaystyle 24\)

Explanation:

The diagonal of a square is also the hypotenuse of a \(\displaystyle 45-45-90\) triangle.

Picture1

Recall how to find the area of a square:

\(\displaystyle \text{Area}=\text{side}^2\)

Now, use the Pythagorean theorem to find the area of the square.

\(\displaystyle \text{side}^2+\text{side}^2=\text{Diagonal}^2\)

\(\displaystyle 2(\text{side})^2=\text{Diagonal}^2\)

\(\displaystyle \text{side}^2=\frac{\text{Diagonal}^2}{2}\)

\(\displaystyle \text{Area}=\text{side}^2=\frac{\text{Diagonal}^2}{2}\)

Substitute in the length of the diagonal to find the area of the square.

\(\displaystyle \text{Area}=\frac{(4\sqrt3)^2}{2}\)

Simplify.

\(\displaystyle \text{Area}=\frac{48}{2}\)

\(\displaystyle \text{Area}=24\)

Example Question #107 : Squares

Find the area of a square if it has a diagonal of \(\displaystyle 2\sqrt3\).

Possible Answers:

\(\displaystyle 12\sqrt2\)

\(\displaystyle 8\sqrt2\)

\(\displaystyle 10\)

\(\displaystyle 6\)

Correct answer:

\(\displaystyle 6\)

Explanation:

The diagonal of a square is also the hypotenuse of a \(\displaystyle 45-45-90\) triangle.

Picture1

Recall how to find the area of a square:

\(\displaystyle \text{Area}=\text{side}^2\)

Now, use the Pythagorean theorem to find the area of the square.

\(\displaystyle \text{side}^2+\text{side}^2=\text{Diagonal}^2\)

\(\displaystyle 2(\text{side})^2=\text{Diagonal}^2\)

\(\displaystyle \text{side}^2=\frac{\text{Diagonal}^2}{2}\)

\(\displaystyle \text{Area}=\text{side}^2=\frac{\text{Diagonal}^2}{2}\)

Substitute in the length of the diagonal to find the area of the square.

\(\displaystyle \text{Area}=\frac{(2\sqrt3)^2}{2}\)

Simplify.

\(\displaystyle \text{Area}=\frac{12}{2}\)

\(\displaystyle \text{Area}=6\)

Example Question #108 : Squares

Find the area of a square if it has a diagonal of \(\displaystyle 3\sqrt2\).

Possible Answers:

\(\displaystyle 9\)

\(\displaystyle 18\)

\(\displaystyle 6\)

\(\displaystyle 12\)

Correct answer:

\(\displaystyle 9\)

Explanation:

The diagonal of a square is also the hypotenuse of a \(\displaystyle 45-45-90\) triangle.

Picture1

Recall how to find the area of a square:

\(\displaystyle \text{Area}=\text{side}^2\)

Now, use the Pythagorean theorem to find the area of the square.

\(\displaystyle \text{side}^2+\text{side}^2=\text{Diagonal}^2\)

\(\displaystyle 2(\text{side})^2=\text{Diagonal}^2\)

\(\displaystyle \text{side}^2=\frac{\text{Diagonal}^2}{2}\)

\(\displaystyle \text{Area}=\text{side}^2=\frac{\text{Diagonal}^2}{2}\)

Substitute in the length of the diagonal to find the area of the square.

\(\displaystyle \text{Area}=\frac{(3\sqrt2)^2}{2}\)

Simplify.

\(\displaystyle \text{Area}=\frac{18}{2}\)

\(\displaystyle \text{Area}=9\)

Example Question #81 : How To Find The Area Of A Square

Find the area of a square if it has a diagonal of \(\displaystyle 2\sqrt7\).

Possible Answers:

\(\displaystyle 14\sqrt2\)

\(\displaystyle 7\sqrt2\)

\(\displaystyle 14\)

\(\displaystyle 7\sqrt3\)

Correct answer:

\(\displaystyle 14\)

Explanation:

The diagonal of a square is also the hypotenuse of a \(\displaystyle 45-45-90\) triangle.

Picture1

Recall how to find the area of a square:

\(\displaystyle \text{Area}=\text{side}^2\)

Now, use the Pythagorean theorem to find the area of the square.

\(\displaystyle \text{side}^2+\text{side}^2=\text{Diagonal}^2\)

\(\displaystyle 2(\text{side})^2=\text{Diagonal}^2\)

\(\displaystyle \text{side}^2=\frac{\text{Diagonal}^2}{2}\)

\(\displaystyle \text{Area}=\text{side}^2=\frac{\text{Diagonal}^2}{2}\)

Substitute in the length of the diagonal to find the area of the square.

\(\displaystyle \text{Area}=\frac{(2\sqrt7)^2}{2}\)

Simplify.

\(\displaystyle \text{Area}=\frac{28}{2}\)

\(\displaystyle \text{Area}=14\)

Example Question #82 : How To Find The Area Of A Square

Find the area of a square if it has a diagonal of \(\displaystyle 3\sqrt7\).

Possible Answers:

\(\displaystyle 63\sqrt2\)

\(\displaystyle 9\sqrt3\)

\(\displaystyle 7\sqrt{10}\)

\(\displaystyle \frac{63}{2}\)

Correct answer:

\(\displaystyle \frac{63}{2}\)

Explanation:

The diagonal of a square is also the hypotenuse of a \(\displaystyle 45-45-90\) triangle.

Picture1

Recall how to find the area of a square:

\(\displaystyle \text{Area}=\text{side}^2\)

Now, use the Pythagorean theorem to find the area of the square.

\(\displaystyle \text{side}^2+\text{side}^2=\text{Diagonal}^2\)

\(\displaystyle 2(\text{side})^2=\text{Diagonal}^2\)

\(\displaystyle \text{side}^2=\frac{\text{Diagonal}^2}{2}\)

\(\displaystyle \text{Area}=\text{side}^2=\frac{\text{Diagonal}^2}{2}\)

Substitute in the length of the diagonal to find the area of the square.

\(\displaystyle \text{Area}=\frac{(3\sqrt7)^2}{2}\)

Simplify.

\(\displaystyle \text{Area}=\frac{63}{2}\)

Example Question #111 : Squares

Find the area of a square if it has a diagonal of \(\displaystyle \sqrt{26}\).

Possible Answers:

\(\displaystyle \frac{13}{2}\)

\(\displaystyle 13\)

\(\displaystyle 26\sqrt2\)

\(\displaystyle 13\sqrt3\)

Correct answer:

\(\displaystyle 13\)

Explanation:

The diagonal of a square is also the hypotenuse of a \(\displaystyle 45-45-90\) triangle.

Picture1

Recall how to find the area of a square:

\(\displaystyle \text{Area}=\text{side}^2\)

Now, use the Pythagorean theorem to find the area of the square.

\(\displaystyle \text{side}^2+\text{side}^2=\text{Diagonal}^2\)

\(\displaystyle 2(\text{side})^2=\text{Diagonal}^2\)

\(\displaystyle \text{side}^2=\frac{\text{Diagonal}^2}{2}\)

\(\displaystyle \text{Area}=\text{side}^2=\frac{\text{Diagonal}^2}{2}\)

Substitute in the length of the diagonal to find the area of the square.

\(\displaystyle \text{Area}=\frac{(\sqrt{26})^2}{2}\)

Simplify.

\(\displaystyle \text{Area}=\frac{26}{2}\)

\(\displaystyle \text{Area}=13\)

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