2 questions!!

[moowithme]

Hi all! I have 2 questions I am very stuck on! Any help would be apprieciated!

Prove: cos(pi-x) = -cosx

and

Prove (1-sinx)(1+cscx) = (cos^2)xcscx

Thanks!!

[NickThissen]

For example for the first one, have you tried using the following identity:

cos(a - b) = cos(a)cos(b) + sin(a)sin(b)


For the second, can you remind me what csc (cosecant) is? I usually only use sin/cos/tan... Was it 1/cos or 1/tan or 1/sin or something?

[moowithme]

csc is 1/sin
Thanks so far!

[NickThissen]

For the second I can't really help you alot without giving away the complete answer.

Try working out the brackets:
(1 - sinx)(1 + 1/sinx)

Then use the well-known identity: sin²x + cos²x = 1

[moowithme]

well i got the first one with no problem with your help, so i think ill be able to get the second! you rock!