Answer: Choice A) 53 degrees
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Check out the attached image. Notice how I'm only focusing on the triangle. I have erased any other extra lines or unneeded info. We have the opposite side 16 and the hypotenuse 20. We'll use the sine ratio and the arcsine function as well. On your calculator, the arcsine function is "arcsin" or it might be labeled "sin^(-1)"
Let x = measure of angle ACB
sine = opposite/hypotenuse
sin(angle ACB) = (height)/(length of ladder)
sin(x) = 16/20
sin(x) = 4/5
sin(x) = 0.8
x = arcsin(0.8)
x = 53.130102354156
x = 53 when rounded to the nearest whole number
So that's why angle ACB is roughly 53 degrees