trig
posted by makaela .
inverse tan x = inverse cos 4/5

inverse cos 4/5
= cos^1 (4/5)
= .6435..
then tan^1 x = .6435...
x = tan .6435...
= .75
or, make a diagram with sides 345
then, if tan^1 x = cos^1 (4/5)
then x = tan (cos^1(4/5) )
= 3/4 or .75