# Help proving trig identities.

• April 1st 2008, 10:47 AM
beetz
Help proving trig identities.
(tan x)(1-cot x)
Here's what I tried:
Sin/cos(1-cos/sin)
--That obviously didn't work

cos x/1-sin x=sec x + tan x
I don't really know how to begin on this one.

Any hints and help is appreciated. Thanks in advance.
• April 1st 2008, 10:56 AM
Jhevon
Quote:

Originally Posted by beetz
(tan x)(1-cot x)
Here's what I tried:
Sin/cos(1-cos/sin)
--That obviously didn't work

of course it didn't work, there's no identity here! what should you be proving?

Quote:

cos x/1-sin x=sec x + tan x
Consider the LHS.

multiply through by $\frac {1 + \sin x}{1 + \sin x}$ and simplify

and use parentheses next time to clarify what you mean. you should have typed (cos x)/(1 - sin x). here it was easy to see what you meant, but it won't always be