View Full Version : Trig identities
sethmich
Mar 20, 2008, 09:28 AM
how do I verify that
(csc(x)/ 1 + csc(x)) - (csc(x)/ 1 - csc(x)) = 2 sec ^2(x)
herz
Mar 20, 2008, 11:16 AM
I could use help with this one too, I tried doing it for practice but I am struggling on what to start with, I tried a few things but nothing was working.
galactus
Mar 20, 2008, 12:46 PM
\frac{csc(x)}{1+csc(x)}-\frac{csc(x)}{1-csc(x)}
Cross multiply:
\frac{csc(x)-csc^{2}(x)-csc(x)-csc^{2}(x)}{(1+csc(x))(1-csc(x))}
\frac{-2csc^{2}(x)}{1-csc^{2}(x)}
Note that 1-csc^{2}(x)=-cot^{2}(x)
\frac{2csc^{2}(x)}{cot^{2}(x)}
Now, can you finish? Write it in terms of sin and cos and you should be able to see it?