Use the sin-1 function to find the angle whose sine is 4/5 or 0.80 then subtract that value into cos(90° - x)
sin-1(4/5) = 53.13°
cos(90° - 53.13°) = cos(36.87°) = 4/5 per the right triangle
We know the opposite side to x° or 53.13° is 4 and the Hypotenuse is 5 because we arw using the sine function which is equal to the opposite/hypotenuse we can use the Pythagorean Theorem to find the missing side.
It is a 3, 4, 5 or Pythagorean Triple right triangle.
SQRT(25 - 16) = SQRT(9) = 3
