Question

How sinθ=sin(180-θ)? (According to this attached image).

Answer 1

(I don't understand how you can do sin(180-theta). Theta is obtuse. Sin is only for right angle, no?

Answer 2

sin (A-B)=sin(A)cos(B)-sin(B)cos(A)
A=180
sin(180)=0
cos(180)=-1
sin(A-B)=0-(sin(B)*(-1))=sin(B)

Answer 3

I know this identity, I just ask about seeing it from the unit circle :(

Answer 4

find co-ordinates of P and P'

Answer 5

y co-ordinate of P gives sin theta
y co-ordinate of P' gives sin (180-theta)

Answer 6

check whether they are equal :)