Answer:
In fact, the AB could be calculated in a quickest way, using Pythagorean theorem. In here, we try to use the property of trigonometry to work out AB.
Before applying trigonometry, in this right triangle we can calculate the remaining angle C:
C = 180 - 90 - A = 180 - 90 - 53.13 = 36.87 deg
We can use cosine formula, but here we use the sine formula for the sake of convenience. We have:
sine(angle measure) = ratio of opposite side over hypotenuse
In detail, sineC = AB/BC
Then, we have: AB = BC x sineC = 15 x sin(36.87 deg) = 9.000002 = ~9 ft
Hope this helps!
:)
Use Pythagorean theorem
a2 + b2 = c2
x2 + 5^2 = 20^2
x^2 + 25 = 400
x^2 = 375
x = 19.4 feet
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