Log in

View Full Version : Prove 8csc^2x-3cot^2=3+5csc^2


Krista_Renae
Apr 3, 2014, 05:22 PM
I have to prove how one side can equal the other but i do not know where to begin with this problem.

I know CSC= 1/sin and COT= cos/sin
I know all of the pythagorean identities as well but i still do not know where to begin with this problem.

ebaines
Apr 4, 2014, 04:49 AM
As usual, first convert the csc and cot functions to their sin and cos equivalents. The trick is then to look for opportunities to use those Pythagorian identities. I'll get you started: note the left hand side is:

\frac 8 {\sin^2x}-\frac {3 \cos^2x}{\sin^2x}

which is equivalent to:

\frac {8 - 8 \cos^2x +5 \cos^2x}{\sin^2x}

Do you see the opportunity to apply 1-\cos^2x = \sin^2x?