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March 26, 2015

March 26, 2015

Posted by **Jill** on Sunday, May 15, 2011 at 2:10pm.

secx-cosx/tanx =sinx

And

1+sinx/cosx+ cox/ 1+sinx=2secx

- trig -
**MathGuru**, Monday, May 16, 2011 at 6:09pmI will show you the first problem to give you an idea how to approach proving trig identities.

Here are a few basic identities that will help:

sinx/cosx = tanx

secx = 1/cosx

cos^2x + sin^2x = 1

Let's put everything into sine and cosine form and work the left hand side:

(secx - cosx)/tanx = sinx

(1/cosx - cosx)/(sinx/cosx) = sinx

(1/cosx - cosx)(cosx)/sinx = sinx

(cosx/cosx - cos^2x)/sinx = sinx

(1 - cos^2x)/sinx = sinx

sin^2x/sinx = sinx

sinx = sinx

And there you have it!

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