If tanA = m/m–1 And tanB = 1/2m – 1, then prove that A –B = π/4.

13

Prove that:

14

If tanA = 5/6 And tanB = 1/11, prove thatA +B = π/4.

15

prove that:

cos² π/4 - sin²

15

prove that:

sin²(n + 1)A – sin²nA = sin(2n + 1)A sinA