tan=opposite / adjacent=sin 78degrees/cos 78 degrees=cot(pi/2-78 degrees)=1/cot 78 degrees
tan 78 degrees=
Using a calculator-make sure it is set to deg. Look at the stop of the screen and it should say DEG and not RAD
input 78
Push "tan"
tan78 degrees=cot(pi/15)=4.70