Mathematics Stack Exchange is a question and answer site for people studying math at any level and professionals in related fields. Join them; it only takes a minute:

Sign up
Here's how it works:
  1. Anybody can ask a question
  2. Anybody can answer
  3. The best answers are voted up and rise to the top

I want to simply the following without use of a calculator: $\displaystyle \frac{2 \tan⁡64°}{1-\tan^2⁡64°}$

At first I thought that this is tangent double angle identity = $\tan(2\times 64°) $

hence $=\tan(128°) $

Is that all? Really?

share|cite|improve this question

$\displaystyle Yup,\ that's\ it.$

share|cite|improve this answer
Double play here! – ncmathsadist Nov 2 '13 at 0:36

Yes, you are correct, $$ \displaystyle \frac{2 \tan⁡x}{1-\tan^2x} = Tan 2x $$. The given problem is absolutely in the given format. Therefore, you directly use this principle to get the required solution that you have already got.

share|cite|improve this answer

Your Answer


By posting your answer, you agree to the privacy policy and terms of service.

Not the answer you're looking for? Browse other questions tagged or ask your own question.