Sign up ×
Mathematics Stack Exchange is a question and answer site for people studying math at any level and professionals in related fields. It's 100% free, no registration required.

Can you please give a hint how to solve this exercise:

$$\log(\tan 22)+ \log(\tan 68)=?\\ \tan22\cdot\tan68=?$$

Thank you!

share|cite|improve this question
Another hint: for this problem in particular you could have worked it out numerically with a calculator; that's not sufficient to give a justification for the answer but the justification is easier to come up with if you know the answer. – Eric Lippert Mar 29 '14 at 14:50
Yes, that's a good hint but imagine I have an exam and don't have a calculator:) – John G. Mar 29 '14 at 14:52

2 Answers 2

up vote 4 down vote accepted

Hint In degree $$\tan(90-x)=\frac{1}{\tan x}$$

share|cite|improve this answer
Sami Ben Romdhane@ Thanks!!! – John G. Mar 29 '14 at 13:49
You're welcome. – user63181 Mar 29 '14 at 13:51


$$22^\circ=90^\circ-68^\circ$$ and $$\tan(90^\circ-x)=\cot x$$

also $$\tan22^\circ\cdot\tan68^\circ\ne0$$

share|cite|improve this answer
Thank you for this hint – John G. Mar 29 '14 at 13:48

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.