Question

How you find `sin2a` using sum identity?

Answer 1

`sin2a=2sinacosa`

Explanation:

`sin2a` can be written as `sin(a+a)` and using sum identity for sine

i.e. `sin(A+B)=sinAcosB+cosAsinB` this becomes

`sin(a+a)=sinacosa+cosasina`

= `sinacosa+sinacosa`

= `2sinacosa`