Sum and Difference Angles Trig Identities

Use sum or difference angles identity to find the exact value for       $$\sin\ \left(-15^o\right)$$  

Assume A and B are positive acute angles. If sinA=15/17 and cosB=4/5, find the cos(A - B).

Write the following expression as the sine, cosine, or tangent of an angle.
cos(175)cos(55)+sin(175)sin(55)

Use the angle sum/difference identity to find the exact value of

Use the angle sum/difference identity to find the exact value of

Complete the following sum or difference identity: $$\cos\ A\cos\ B\ -\ \sin\ A\sin\ B=$$ ​ (a)  

Complete the following sum or difference identity: $$\cos\ A\cos\ B\ +\ \sin\ A\sin\ B=$$ ​ (a)  

Complete the following sum or difference identity: $$\frac{\tan\ A\ -\ \tan\ B}{1+\tan A\tan B}=$$ ​ (a)  

Complete the following sum or difference identity: $$\sin\ A\cos\ B\ -\ \cos\ A\sin\ B=$$ ​ (a)  

Complete the following sum or difference identity: $$\sin\ A\cos\ B\ +\ \cos\ A\sin\ B=$$ ​ (a)