Question

solve this question....​

Answer 1

hope it helps ^_^
Thank you !

Answer 2

If sinΦ = 1/2

Then Φ = 30°

LHS = 4cos³Φ - 3cosΦ = 4cos³30° - 3cos30 = 4×($\frac{\sqrt{3} }{2}$)³  - 3× $\frac{\sqrt{3} }{2}$

= 4 × $\frac{3\sqrt{3} }{8}$ - $\frac{3\sqrt{3} }{2}$

= $\frac{\sqrt{3} }{2} -\frac{\sqrt{3} }{2}$

= 0 = RHS

Hence Proved