Basic Geometry : Right Triangles

Study concepts, example questions & explanations for Basic Geometry

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Example Questions

Example Question #1181 : Plane Geometry

Triangles 3

Refer to the above diagram.

True or false: 

Possible Answers:

False

True

Correct answer:

True

Explanation:

The distance from the origin to  is the absolute value of the -coordinate of , which is . Similarly, , and . Also, since the axes intersect at right angles,  and  are both right, and, consequently, congruent. 

According to the Side-Angle-Side Similarity Theorem (SASS), if two sides of a triangle are in proportion to the corresponding sides of a second triangle, and their included angles are congruent, the triangles are similar. 

We can test the proportion statement 

by substituting:

Test the truth of this statement by comparing their cross products:

The cross-products are equal, making the proportion statement true, so two pairs of sides are in proportion. Also, their included angles   and  are congruent. This sets up the conditions of SASS, so .

 

 

Example Question #11 : Right Triangles

Triangles

Refer to the above figure. 

True, false, or inconclusive: .

Possible Answers:

False

True

Inconclusive

Correct answer:

True

Explanation:

 is an altitude of , so it divides the triangle into two smaller triangles similar to each other - that is, if we match the shorter legs, the longer legs, and the hypotenuses, the similarity statement is

.

Example Question #1 : How To Find The Length Of The Side Of A Right Triangle

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What is the length of the remaining side of the right triangle?

Possible Answers:

Correct answer:

Explanation:

Rearrange the Pythagorean Theorem to find the missing side. The Pythagorean Theorem is:

 where  is the hypotenuse and and  are the sides.

Example Question #2 : How To Find The Length Of The Side Of A Right Triangle

The hypotenuse of a right triangle is 26 in and one leg is 10 in.  What is the sum of the two shortest sides?

Possible Answers:

Correct answer:

Explanation:

We use the Pythagorean Theorem so the problem to solve becomes where = unknown leg length

So and

The sum of the two legs becomes

Example Question #3 : How To Find The Length Of The Side Of A Right Triangle

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Possible Answers:

Correct answer:

Explanation:

Example Question #1 : How To Find The Length Of The Side Of A Right Triangle

Find the length of the unknown side, , of the right triangle below.

Triangle_a_9_12

Possible Answers:

Correct answer:

Explanation:

We need to use the Pythagorean Theorem, which says that .

Since we need to find the length of 'a', we can just solve for 'a'.

In our case, c = 12 and b = 9.

Thus, .

Example Question #2 : How To Find The Length Of The Side Of A Right Triangle

Find the missing leg of the right triangle when one of the legs is  and the hypotenuse is .

Possible Answers:

Correct answer:

Explanation:

In order to find the missing side of a right triangle you must use one of two things:

1. Pythagorean Theorem

2. Trigonometry.

Since we only know what the side lengths are we must use the Pythagorean Theorem.

a=4, b=x, and c=5

So the missing side length is 3

Example Question #1 : How To Find The Length Of The Side Of A Right Triangle

Given that the hypotenuse of a right triangle is  and one side is , find the other side length.

Possible Answers:

Correct answer:

Explanation:

To find the length of the missing side, you can either use the pythagorean theorm or realize this is a case of a special right triangle with sides .

Thus, the other side length is .

Example Question #2 : How To Find The Length Of The Side Of A Right Triangle

Find the length of the missing side.

1

Possible Answers:

Correct answer:

Explanation:

13

Recall the Pythagorean Theorem for a right triangle:

Since the missing side corresponds to side , rewrite the Pythagorean Theorem and solve for .

Now, plug in values of  and  into a calculator to find the length of side . Round to  decimal places.

Example Question #1 : How To Find The Length Of The Side Of A Right Triangle

Find the length of the missing side.

2

Possible Answers:

Correct answer:

Explanation:

13

Recall the Pythagorean Theorem for a right triangle:

Since the missing side corresponds to side , rewrite the Pythagorean Theorem and solve for .

Now, plug in values of  and  into a calculator to find the length of side . Round to  decimal places.

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