Question

if sin theta = -4/5 is in 3rd quadrant then find sin2theta?

Answer 1

theta=@
sin2@=2sin@cos@__________(1)

sin@=-4/5

now from equation (1)

sin^2@=16/25

1-cos^2@=16/25

cos@=3/5

now

sin2@=2*3/5*-4/5

sin2@= -24/25