Question

csctheta= -5/12, tantheta>0, find cos 2theta
a)-4sqrt21/25
b)4sqrt21/25
c)17/25
d)-17/25

Answer 1

Maybe you can use the relation,
\[\cos(2\theta)=1-\frac{2}{\csc^2(\theta)}\]

Answer 2

I think not, you mean cos^2theta or cos(2*theta)?

Answer 3

cos2*theta

Answer 4

Ok, then the formula should be correct.