Right angle Trigonometry, please help me solve and explain!

Answer:
theta = arctan 8/5 = 58 degrees
Step-by-step explanation:
The tangent function relates the angle theta to the two side lengths 5 and 8:
tan theta = 8/5 We need to find the angle, theta.
Using a calculator with the inverse tangent funtion built-in, we find that the angle theta is
theta = arctan 8/5 = 58 degrees.