Trigonometry : Right Triangles

Study concepts, example questions & explanations for Trigonometry

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Example Questions

Example Question #2 : 45 45 90 Triangles

In a  triangle, if one leg is . What is the measure of the hypotenuse? 

Possible Answers:

Correct answer:

Explanation:

One option is to use the Pythagorean Theorem.

Since we have an isosceles triangle, both legs must be congruent.

Plug in to get your answer.

 

Or, you can remember the 45-45-90 identity, which states that the hypotenuse is  times the leg. 

Example Question #2 : 45 45 90 Triangles

In a 45-45-90 triangle, if the hypotenuse is 10, what is the perimeter of the triangle?

Possible Answers:

Correct answer:

Explanation:

Write the Pythagorean Theorem.

In a 45-45-90 triangle, the length of the legs are equal, which indicates that:

Rewrite the formula and substitute the known sides.

The lengths of the triangle are:  

Sum the three lengths for the perimeter.

Example Question #2 : 45 45 90 Triangles

One side of a -- triangle has a length of 3. Which cannot be the length of one of the other sides?

Possible Answers:

Correct answer:

Explanation:

If 3 is one of the legs, then the hypotenuse is .

If 3 is the hypotenuse, then the legs are or equivalently

Example Question #3 : 45 45 90 Triangles

The hypotenuse of a -- triangle is 4. What is the length of each of the legs?

Possible Answers:

Correct answer:

Explanation:

Divide the length of the hypotenuse by to get the length of the legs:

Example Question #3 : 45 45 90 Triangles

The perimeter of a square is 56 feet. What is the length of the diagonal in feet?

Possible Answers:

There is not enough information

Correct answer:

Explanation:

The perimeter of a square can be found using the formula , where P is the perimeter and s is the length of the side of the square.

The diagonal of a square forms the hypotenuse of a 45-45-90 triangle, where each leg is the side of the square. In a 45-45-90 triangle, the ratio of the hypotenuse to the leg is , so the diagonal of this square is .

Example Question #11 : Right Triangles

Find the value of 

20

Possible Answers:

Correct answer:

Explanation:

Solving this problem begins with realizing that all three of our triangles are not only right triangles but isosceles and are therefore 45-45-90 triangles.  That means in each triangle to get from the length of a leg to the length of the hypotenuse, we simply multiply by .  Therefore, the hypotenuse of our bottom triangle is

However, the hypotenuse of the bottom triangle is also the leg of the middle triangle.  To find the hypotenuse of this triangle, we simply repeat the process.

However, again the hypotenuse of the middle triangle is also the leg of the upper triangle.  To find , the hypotenuse of the upper triangle, we simply repeat the process one last time.

Example Question #11 : Right Triangles

In a 30-60-90 triangle, the length of the side opposite the  angle is . What is the length of the hypotenuse? 

Possible Answers:

Correct answer:

Explanation:

By definition, the length of the hypotenuse is twice the length of the side opposite the angle.

Recall that the hypotenuse is the side opposite the  angle. 

Thus, using the equation below, where ss represents the short side (that opposite the angle) we get: 

Plugging in our values for the short side we find the hypotenuse as follows:

Example Question #12 : Right Triangles

A triangle has three angles ,  and  such that  and . The side opposite to  measures  units in length. How long is the side opposite of ?

Possible Answers:

Correct answer:

Explanation:

A triangle with a  angle relation is a , ,  degree triangle. The side opposite the smallest angle of a triangle is the shortest side, of length . The side opposite the largest angle is the longest side, measuring twice the length of the shortest side for this triangle,  units.

Therefore, to make the above statement true .

Example Question #2 : 30 60 90 Triangles

Triangle  is equilateral with a side length of .

What is the height of the triangle?

Possible Answers:

Correct answer:

Explanation:

An equilateral triangle has internal angles of 60°, so the sin of one of those angles is equivalent to the height of the triangle divided by the side length, 

so..

Example Question #2 : 30 60 90 Triangles

In a  triangle, the side opposite the  degree angle is . How long is the side opposite the  degree angle? 

Possible Answers:

Correct answer:

Explanation:

Based on the 30-60-90 identity, the measure of the side opposite the 30 degree angle is doubled to get the hypotenuse. 

Therefore,

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