Question

help with trig identities!! (attached)

Answer 1

if we multiply andf divide it with 2 then we can use one identity,i.e,
2cosAsinB=sin(A+B)-sin(A-B)

=2*1/2(cosx/5)(sinx/5)
using identity,we get
=1/2sin(x/5+x/5)-sin(x/5-sinx/5)
=1/2sin(x/5+x/5)-0 (sin0=0)
=1/2sin(2x/5)
hence,true.