Question

Please help me please


`2 \sin7 \alpha .cos2 \alpha = sin9 \alpha + sin5 \alpha`
it's a prove that​

Answer 1

they are identical. proved below.

Explanation:

• formula:
  `sin(t)+sin(s) = 2sin((t+s)/(2) )cos((t-s)/(2) )`

using the formula to proof:

`sin9a+sin5a`

`2sin((9+5)/(2))* cos((9-5)/(2))`

`2sin7a * cos2a`

True. proved that they are identical.