# Math Help - trigonometry (tan and cos)

1. ## trigonometry (tan and cos)

Hello!

tanx = 5/12, we have to get a cos value, and calculate the angle x.

I was trying this several times but i always get error on the calculator.

2. If tan a = 5/12, then let y = 5u and x = 12u. Then the hypotenuse = $(5u)^2 + (12u)^2 = (5^2 + 12^2)u^2 = 13^2u^2 = (13u)^2$. Thus, the cosine is $\frac{12u}{13u} = \frac{12}{13}$. To calculate the angle, type $\tan^{-1} \left(\frac{5}{12}\right)$.