The tangent of the acute angle of a rectangular trapezoid is 5/3. Find its larger base if the smaller base is equal to height and equal to 40

We introduce the notation and draw the height BE perpendicular to the CD as shown in the figure.
By condition AB = BE = 40
Then ABED is a square (all angles are straight and all sides are equal).
The triangle BCE is rectangular, therefore
by definition, tgC = BE / EC = 5/3.
40 / EC = 5/3 => EC = 40 * 3/5 = 24
DC = DE + EC
DE = AB (by definition of a square)
DC = 40 + 24 = 64
Answer: DC = 64

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