Question

Which sum or difference identity could be used to prove that sin(pi+q)=-sinq

Answer 1

see explanation

Explanation:

Using the Addition formula for sine

sin(x + y) = sinxcosy + cosxsiny

and sinπ = 0, cosπ = - 1, then

sin(π + q)

= sinπcosq + cosπsinq

= 0. cosq + (- 1)sinq

= 0 - sinq

= - sinq ← as required