Posted by **Josh** on Thursday, May 23, 2013 at 2:56pm.

TRIG Identities, Gr. 12:

Prove:

cot4x=1-tan^2x/2tan2x

- trig -
**Steve**, Thursday, May 23, 2013 at 3:02pm
just apply the double-angle formula for tan(2x) and take the reciprocal

- trig -
**Josh**, Thursday, May 23, 2013 at 3:13pm
okay, thank you, would that still apply if it was cot4x=1-tan^2(2x)/2tan2x? because ive got the right side for this one but the cot4x is throwing me off, how would you solve that side?

- trig -
**Steve**, Thursday, May 23, 2013 at 3:17pm
you are exactly right

tan(4x) = 2tan2x/(1-tan^2(2x))

so, cot(4x) is the reciprocal, as needed.

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