3. Find the exact value of each of the following. Do not use a calculator — answers given as decimals will not receive credit. A.

Part I:
Find two common angles that either add up to or differ by . Rewrite this problem as the cosine of either a sum or a difference of those two angles. (2 points)

Part II:
Evaluate the expression. (4 points)

B.

Part I:
Find two common angles that either add up to or differ by . Rewrite this problem as the tangent of either a sum or a difference of those two angles. (2 points)

Part II:
Evaluate the expression. (4 points)

C.

Part I:
Find two common angles that either add up to or differ by . Rewrite this problem as the sine of either a sum or a difference of those two angles. (2 points)

Part II:
Evaluate the expression. (4 points)

D.

Part I:
Find two common angles that differ by . Rewrite this problem as the cotangent of a difference of those two angles. (2 points)

Part II:
Evaluate the expression. (4 points)