Remember SOH CAH TOA?
Since you have the adjacent and hypotenuse, you use CAH (cos(t) = A/H, where t is the angle). If you're trying to find the angle, its a simple matter of using inverse operations to find the angle.
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Answer:
cos(t)=50/63.262527
acos(cos(t)) = acos(50/63.262527)
t = acos(50/63.262527)
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