How do i find cos[arctan(3/5)] ?
I know I need to set up some kind of triangle diagram, but I don't know how or what to do next. I am not allowed to use a calculator.
Thanks to anyone that tries to help me.
--Cori
Let $\displaystyle \arctan \left( \frac {3}{5} \right) = \theta \implies \tan \theta = \frac {3}{5}$
Thus we can set up a right-triangle and label one of the acute angles "theta" and fill in the sides accordingly. (tangent = opposite/adjacent). we can use Pythagoras' theorem to find the length of the hypotenuse, which here is $\displaystyle \sqrt {34}$
Thus we can say, $\displaystyle \cos \left[ \arctan \left( \frac {3}{5} \right) \right] = \cos \theta = $ ?
It shouldn't be too hard for you to finish, right?