# unit circle

• Nov 8th 2008, 03:29 PM
FinalFantasy9291
unit circle
how do you find tan(cos-1(1/3)) if it's not on the unit circle?
• Nov 8th 2008, 03:46 PM
Plato
Let $\phi = \arccos (1/3)$ so $\cos (\phi ) = 1/3$.
Look at the diagram. What is $\tan (\phi ) = ?$