The height of the pole is 18 & the height from the top of the pole to the ground is 15. So you’ve got your hypotenuse (18) & ur opposite (from the angle: 15). That gives you Sin(theta). So sin(theta)= 15/18. Divide 15/18 & get .83. Use the inverse of sin (sin^-1(.83)) to get that the angle is 56.1. Hopefully that’s correct
