Question

If sin A = `12/13`, find sin 3A.

Answer 1

If sin A = `12/13`

We know that sin 3A = 3 sin A – 4 sin³ A

`= 3(12/13) - 4(12/13)^3`

`= 12/13 [3 - 4 xx 12/13 xx 12/13]`

`= 12/13 [3 - 576/169]`

`= 12/13[(507 - 576)/169]`

`= 12/13 [(-69)/169]`

`= (- 828)/2197`