Basic Geometry : How to find the length of the side of a right triangle

Study concepts, example questions & explanations for Basic Geometry

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Example Questions

Example Question #1191 : Plane Geometry

Find the length of the missing side.

5

Possible Answers:

\(\displaystyle 23.64\)

\(\displaystyle 19.58\)

\(\displaystyle 22.91\)

\(\displaystyle 24.21\)

Correct answer:

\(\displaystyle 22.91\)

Explanation:

13

Recall the Pythagorean Theorem for a right triangle:

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

Since the missing side corresponds to side \(\displaystyle b\), rewrite the Pythagorean Theorem and solve for \(\displaystyle b\).

\(\displaystyle b^2=c^2-a^2\)

\(\displaystyle b=\sqrt{c^2-a^2}\)

Now, plug in values of \(\displaystyle c\) and \(\displaystyle a\) into a calculator to find the length of side \(\displaystyle b\). Round to \(\displaystyle 2\) decimal places.

\(\displaystyle b=\sqrt{25^2-10^2}=\sqrt{525}=22.91\)

Example Question #12 : How To Find The Length Of The Side Of A Right Triangle

Find the length of the missing side.

6

Possible Answers:

\(\displaystyle 19.33\)

\(\displaystyle 24.36\)

\(\displaystyle 21.93\)

\(\displaystyle 25.91\)

Correct answer:

\(\displaystyle 21.93\)

Explanation:

13

Recall the Pythagorean Theorem for a right triangle:

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

Since the missing side corresponds to side \(\displaystyle b\), rewrite the Pythagorean Theorem and solve for \(\displaystyle b\).

\(\displaystyle b^2=c^2-a^2\)

\(\displaystyle b=\sqrt{c^2-a^2}\)

Now, plug in values of \(\displaystyle c\) and \(\displaystyle a\) into a calculator to find the length of side \(\displaystyle b\). Round to \(\displaystyle 2\) decimal places.

\(\displaystyle b=\sqrt{25^2-12^2}=\sqrt{481}=21.93\)

Example Question #13 : How To Find The Length Of The Side Of A Right Triangle

Find the length of the missing side.

7

Possible Answers:

\(\displaystyle 12.36\)

\(\displaystyle 17\)

\(\displaystyle 20\)

\(\displaystyle 19.55\)

Correct answer:

\(\displaystyle 20\)

Explanation:

13

Recall the Pythagorean Theorem for a right triangle:

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

Since the missing side corresponds to side \(\displaystyle b\), rewrite the Pythagorean Theorem and solve for \(\displaystyle b\).

\(\displaystyle b^2=c^2-a^2\)

\(\displaystyle b=\sqrt{c^2-a^2}\)

Now, plug in values of \(\displaystyle c\) and \(\displaystyle a\) into a calculator to find the length of side \(\displaystyle b\). Round to \(\displaystyle 2\) decimal places.

\(\displaystyle b=\sqrt{25^2-15^2}=\sqrt{400}=20\)

Example Question #14 : How To Find The Length Of The Side Of A Right Triangle

Find the length of the missing side.

8

Possible Answers:

\(\displaystyle 17.75\)

\(\displaystyle 19.39\)

\(\displaystyle 16.81\)

\(\displaystyle 18.25\)

Correct answer:

\(\displaystyle 17.75\)

Explanation:

13

Recall the Pythagorean Theorem for a right triangle:

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

Since the missing side corresponds to side \(\displaystyle b\), rewrite the Pythagorean Theorem and solve for \(\displaystyle b\).

\(\displaystyle b^2=c^2-a^2\)

\(\displaystyle b=\sqrt{c^2-a^2}\)

Now, plug in values of \(\displaystyle c\) and \(\displaystyle a\) into a calculator to find the length of side \(\displaystyle b\). Round to \(\displaystyle 2\) decimal places.

\(\displaystyle b=\sqrt{18^2-3^2}=\sqrt{315}=17.75\)

Example Question #15 : How To Find The Length Of The Side Of A Right Triangle

Find the length of the missing side.

9

Possible Answers:

\(\displaystyle 21.57\)

\(\displaystyle 13.69\)

\(\displaystyle 17.98\)

\(\displaystyle 16.58\)

Correct answer:

\(\displaystyle 16.58\)

Explanation:

13

Recall the Pythagorean Theorem for a right triangle:

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

Since the missing side corresponds to side \(\displaystyle b\), rewrite the Pythagorean Theorem and solve for \(\displaystyle b\).

\(\displaystyle b^2=c^2-a^2\)

\(\displaystyle b=\sqrt{c^2-a^2}\)

Now, plug in values of \(\displaystyle c\) and \(\displaystyle a\) into a calculator to find the length of side \(\displaystyle b\). Round to \(\displaystyle 2\) decimal places.

\(\displaystyle b=\sqrt{18^2-7^2}=\sqrt{275}=16.58\)

Example Question #16 : How To Find The Length Of The Side Of A Right Triangle

Find the length of the missing side.

10

Possible Answers:

\(\displaystyle 14.52\)

\(\displaystyle 17.99\)

\(\displaystyle 15.59\)

\(\displaystyle 16.23\)

Correct answer:

\(\displaystyle 15.59\)

Explanation:

13

Recall the Pythagorean Theorem for a right triangle:

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

Since the missing side corresponds to side \(\displaystyle b\), rewrite the Pythagorean Theorem and solve for \(\displaystyle b\).

\(\displaystyle b^2=c^2-a^2\)

\(\displaystyle b=\sqrt{c^2-a^2}\)

Now, plug in values of \(\displaystyle c\) and \(\displaystyle a\) into a calculator to find the length of side \(\displaystyle b\). Round to \(\displaystyle 2\) decimal places.

\(\displaystyle b=\sqrt{18^2-9^2}=\sqrt{243}=15.59\)

Example Question #17 : How To Find The Length Of The Side Of A Right Triangle

Find the length of the missing side.

11

Possible Answers:

\(\displaystyle 18.92\)

\(\displaystyle 14.62\)

\(\displaystyle 12.68\)

\(\displaystyle 16.97\)

Correct answer:

\(\displaystyle 16.97\)

Explanation:

13

Recall the Pythagorean Theorem for a right triangle:

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

Since the missing side corresponds to side \(\displaystyle b\), rewrite the Pythagorean Theorem and solve for \(\displaystyle b\).

\(\displaystyle b^2=c^2-a^2\)

\(\displaystyle b=\sqrt{c^2-a^2}\)

Now, plug in values of \(\displaystyle c\) and \(\displaystyle a\) into a calculator to find the length of side \(\displaystyle b\). Round to \(\displaystyle 2\) decimal places.

\(\displaystyle b=\sqrt{18^2-6^2}=\sqrt{288}=16.97\)

Example Question #18 : How To Find The Length Of The Side Of A Right Triangle

Find the length of the missing side.

12

Possible Answers:

\(\displaystyle 16\)

\(\displaystyle 15\)

\(\displaystyle 17\)

\(\displaystyle 14\)

Correct answer:

\(\displaystyle 15\)

Explanation:

13

Recall the Pythagorean Theorem for a right triangle:

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

Since the missing side corresponds to side \(\displaystyle b\), rewrite the Pythagorean Theorem and solve for \(\displaystyle b\).

\(\displaystyle b^2=c^2-a^2\)

\(\displaystyle b=\sqrt{c^2-a^2}\)

Now, plug in values of \(\displaystyle c\) and \(\displaystyle a\) into a calculator to find the length of side \(\displaystyle b\). Round to \(\displaystyle 2\) decimal places.

\(\displaystyle b=\sqrt{17^2-8^2}=\sqrt{225}=15\)

Example Question #19 : How To Find The Length Of The Side Of A Right Triangle

Tri 3

Given the right triangle above, find the value of \(\displaystyle x\).

Possible Answers:

\(\displaystyle 1\)

\(\displaystyle 4\)

\(\displaystyle 9\)

\(\displaystyle 3\)

\(\displaystyle 2\)

Correct answer:

\(\displaystyle 3\)

Explanation:

To find the length of the side x, we must use the Pythagorean Theorem

\(\displaystyle a^2+b^2=c^2\).  

However, this time since we are given the value of the hypotenuse, we will solve for side b rather than c.  

So, when we plug the given values into the formula, the equation looks like 

\(\displaystyle 4^2+b^2=5^2\) 

which can be simplified to 

\(\displaystyle 16+b^2=25\).  

Next, solve for b and we get a final answer of 

\(\displaystyle b=\sqrt{9}=3\).  

This particular example is a Pythagorean triple, or a right triangle with 3 whole number values, so it is a good one to remember.

Example Question #20 : How To Find The Length Of The Side Of A Right Triangle

Tri 5

Given the right triangle above, find the length of the missing side.

Possible Answers:

\(\displaystyle 38\)

\(\displaystyle 40\)

\(\displaystyle 28\)

\(\displaystyle 52\)

\(\displaystyle 31\)

Correct answer:

\(\displaystyle 40\)

Explanation:

To find the length of the side x, we must use the Pythagorean Theorem

\(\displaystyle a^2+b^2=c^2\).  

However, this time since we are given the value of the hypotenuse, we will solve for side b rather than c.  

So, when we plug the given values into the formula, the equation looks like 

\(\displaystyle 9^2+b^2=41^2\) 

which can be simplified to 

\(\displaystyle 81+b^2=1681\).  

Next, solve for b and we get a final answer of 

\(\displaystyle b=\sqrt{1600}=40\).  

This particular example is a Pythagorean triple, or a right triangle with 3 whole number values, so it is a good one to remember.

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