Use the diagram to answer the question. Triangle R S T. Segment R S measures 10 units Segment R T measures 8 units. Angle T is a right angle. What is the measure of ∠R?

Answer 1

review your basic trig functions and it is clear that
cos R = 8/10
so, ...

Answer 2

If you need the answer specifically it's 36.869. But if you need the answer rounded the answer is 36.9.