A 21-foot ladder is leaning against a building. The base of the ladder is 7 feet from the base of a building. To the nearest degree, what is the measure of the angle that the ladder makes with the ground?

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Answer 1 · 2018-03-07T01:06:49

#alpha= 71°#:

Consider the diagram:
enter image source here

From trigonometry we have:

#cos alpha = 7/21 #

#7=21cos(alpha)#

and:

#alpha=arc cos(7/21)=70.5~~71^@#