Video Assignment 17

1. Find the exact value of each expression.

a. ( )1712cos  b. ( )512sin



c. ( )12sin − d. ( )12cos



e. 5 5 18 18 18 18

sin cos cos sin   + f. 2 8 2 8 15 15 15 15

cos cos sin sin   −

f. 5 5 18 9 18 9

cos cos sin sin   + f. 8 8 21 21 21 21

sin cos cos sin   −

2. Show that each of the following is true.

a. ( )2sin cosx x + = b. ( )32sin cosx x

+ = −

c. ( )cos cosx x − = − d. ( )2cos sinx x − =

e. ( )4 tan 1

tan 1 tan

x x

x 

+ + =

− f. ( )tan tanx x − = −

Math 347 – Skills for Trigonometry

Video Assignment 17 – Sum and Difference Formulas

Name _________________________

Watch the video for this assignment available on Canvas. As you watch the video, copy the work done for

each problem exactly as it was shown. Then complete the similar problems showing the same steps.

3. Find the exact value of ( )sin A B+ , ( )cos A B+ and ( )tan A B+ , given that

a. 4 5

sin A = with in QIIA and b. 1 2

sin A = − with in QIIIA

7 25

cos B = − with in QIIIB 3 5

cos B = with in QIVB

c. 5 12

tan A = − with in QIVA d. 4 3

tan A = − with in QIIA

sec 3B = − with in QIIIB 2 3

csc B = with in QIB

4. Prove each identity.

a. ( )cos

1 tan tan cos cos

A B A B

A B

− = + b.

( )sin tan tan

cos cos

A B A B

A B

− = −