Trigonometry
posted by AwesomeGuy .
Height of a mountain
While traveling across flat land, you notice a mountain directly in front of you. The angle of elevation to the peak is 2.5°. After you drive 18 miles closer to the mountain, the angle of elevation is 10°. Approximate the height of the mountain.

draw a diagram. if the height is h,
h/tan2.5° = h/tan10° + 18