Unit 9 Lesson 6 Cofunctions

In ∆ABC, where ∠C is a right angle,

cos A= √21 ⁄ 5 . What is sin B?

• √21 ⁄ 5

• √21 ⁄ 2

• 2 ⁄ 5

• 5 ⁄ √21

In ∆ABC, the complement of ∠B is ∠A. Which statement is always true?

• tan∠A = tan∠B

• sin∠A = sin∠B

• cos∠A = tan∠B

• sin∠A = cos∠B

Which expression is always equivalent to sin x when 0°< x < 90°?

• cos(90°−x)

• cos(45°−x)

• cos(2x)

• cos x

In right triangle ABC, m∠C =90°. If cos B= 5 ⁄ 13, which function also equals 5 ⁄ 13?

• tanA

• tanB

• sinA

• sinB

In scalene triangle ABC shown in the diagram above, m∠C = 90°. Which equation is always true?

• sinA=sinB

• cosA=cosB

• cosA=sinC

• sinA =cosB

If cos 32° = sinx, find the number of degrees in the measure of acute angle x.

• 32

• 78

• 58

• 68

Find the value of R that will make the equation sin73°=cosR true when 0°<R<90°.

• 27

• 17

• 45

• 73

Which value of x satisfies the equation sin(3x+5)°=cos(4x+1)°?

• 30

• 24

• 12

• 4

If sin(2x+7)°=cos(4x−7)°, what is the value of x?

• 7

• 15

• 21

• 30

In a right triangle,

sin(40−x)°=cos(3x)°.

What is the value of x?

• 10

• 15

• 20

• 25