cot=adjacent side to right angle/ opposite side to right angle=cos 39 degrees/sin 39 degrees=tan(pi/2-39 degrees)=1/tan 39 degrees
cot 39 degrees=
Using a calculator-make sure it is set to deg. Look at the top of the screen and it should say DEG and not RAD
input 39
Push "cot"
tan 39 degrees=1.23
The other option is to use a standard trig chart
http://math2.org/math/trig/tables.htm
Find the cot for 39 degrees