Answer:
3. cos(68°)
4. sin(35°)
5. sin(75°)
6. cos(53°)
Explanation:
You want to rewrite the sine of an angle in terms of cosine, and vice versa.
Complements
You know from problem 1, for example, that cos(J) = sin(K), where J and K are the (complementary) acute angles in a right triangle. That is the relation you use for problems 3–6.
3.
sin(22°) = cos(90°-22°) = cos(68°)
4.
cos(56°) = sin(90°-56°) = sin(34°)
5.
cos(15°) = sin(90°-15°) = sin(75°)
6.
sin(37°) = cos(90°-37°) = cos(53°)