This is a simple trig right triangle function problem.
cos(theta) = adjacent/hypotenuse
cos(theta) = 7 ft/15 ft
= 0.46666
======In radians.
0.46666 * (180 degrees/pi)
= 26.74 degrees
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A 15 foot ladder is leaning against the side of a house so that the distance on the ground between the base of the ladder and the house is 7 feet. What is the angle at the base of the ladder is making with the ground?