We can draw Triangle OAT separately. Shown below:
We want to find the angle "x", which is Angle TOA.
With respect to angle x, we know the adjacent side (31) and the hypotenuse (50). The trig ratio cosine relates adjacent to hypotenuse.
Thus, we can write:
We can use a calculator and take the inverse cosine and figure out x. Shown below:
The answer is: