1. Double Angle Formulas

4. Let sinA=1/5 with A in QI. Find sin(2A).

7. Find sin(90°) using a double angle formula.

8. Simplify 2sin30°cos30°.

11. Simplify cos 2 15°–sin 2 15°.

12. Derive an alternative form of the identity cos(2A)=cos 2 A–sin 2 A.

14. The identity with its alternative forms.

15. Suppose that cos x =1/  10 with x  Q IV, find sin(2x) and cos(2x).

19. Simplify 2cos 2 105°–1.

20. Prove that (cos x – sin x)(cos x + sin x)=cos(2x)

37. Derive a double angle formula for the tangent function.

51. Given cos  =1/  10 and x  QIV, find tan(2  ).

55. Given csc t =  7 with t in QII, find sin(2t) and cos(2t).