To find the measure of Angle A, we'll need to use a trigonometric function.
Remember: SOH-CAH-TOA
Looking from Angle A, we know the opposite side and the hypotenuse. Therefore, we should use the sine function.
sin(A) = 9 / 18
---To solve for A, you'll need to use the inverse sin function on your calculator. It should look like so: sin^-1()
The inverse sin of 1/2 = 30
Answer: first option, 30 degrees
Hope this helps!
