inverse tan x = inverse cos 4/5

Answer 1

inverse cos 4/5
= cos^-1 (4/5)
= .6435..
then tan^-1 x = .6435...
x = tan .6435...
= .75

or, make a diagram with sides 3-4-5
then, if tan^-1 x = cos^-1 (4/5)
then x = tan (cos^-1(4/5) )
= 3/4 or .75