A. Maths trigo question

• apologist

  30 Apr 11, 03:25

  How do u find the value of sin 12° + sin 48° - sin 72° without calculator? [answer is zero]

• wee_ws

  30 Apr 11, 07:05

  Hi,

    Consider the fact that

    sin P - sin Q = 2 cos ((P + Q)/2) sin ((P - Q)/2).

    Thanks.

  Cheers,
  Wen Shih

• wee_ws

  30 Apr 11, 07:10

  Hi,

    Another alternative is to consider these facts:

    1. sin 48° = sin (60° - 12°),

    2. the identity of sin (A - B),

    3. sin 72° = sin (60° + 12°),

    4. the identity of sin (A + B).

    Thanks.

  Cheers,
  Wen Shih

• apologist

  1 May 11, 01:44

  I got it now! THanks a bunch Wen Shih!!!