Author Topic: Proving trig equations [solved] (Read 736 times) Tweet Share

Richiie · « **on:** May 14, 2010, 08:14:19 pm »

Hey everyone,

I'm lost on how to prove this; sec(x)-tan(x) = 2cot(2x).

Any help would be appreciated.

Richiie · « **Reply #1 on:** May 14, 2010, 08:18:01 pm »

dw, friend told me the wrong question, lol. it was cot(x), not sec(x)

m@tty · « **Reply #2 on:** May 14, 2010, 08:20:15 pm »

$RHS=2\cot(2x)=\frac{2}{\tan(2x)}$

$=2\cdot \frac{1-tan^2(x)}{2\tan(x)}$

$=\frac{1}{\tan(x)} - \frac{\tan^2(x)}{\tan(x)}$

$=\cot(x)-\tan(x)=LHS$

QED.

EDIT:

Quote from: Richiie on May 14, 2010, 08:18:01 pm

dw, friend told me the wrong question, lol. it was cot(x), not sec(x)

haha, that sucks.

Richiie · « **Reply #3 on:** May 14, 2010, 08:25:08 pm »

haha, well thank you for demonstrating.

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Author Topic: Proving trig equations [solved] (Read 736 times) Tweet Share

Richiie

Proving trig equations [solved]

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