Sec x = 4
Then cos x = 1/4
This implies the adjacent is 1 and the hypotenuse is 4
Use the pythagorean theorem to find the opposite:
1^2 + b^2 = 4^2
1+b^2 = 16
b^2 = 15
b = sqrt 15
So since Sinx = opp/hyp
sin = sqrt15/4
And Tan = sin / cos
tan x = (sqrt15)/4 ÷ 1/4 = sqrt 15