The diagonal AC divides the trapezoid ABCD into two similar triangles ABC and ACD, BC = 8cm

The diagonal AC divides the trapezoid ABCD into two similar triangles ABC and ACD, BC = 8cm, AD = 18cm. Find the length of the diagonal AC

By condition, the AC diagonal divides the trapezoid into two similar triangles.

Triangle ABC ~ ACD.

The angle АСD is equal to the angle СD as criss-crossing angles at the intersection of parallel lines ВС and АD of the secant АС. The angle D of the triangle CAD cannot be equal to the angle B of the triangle ABC, then the angle ABC = ACD, and the angle BAC = ADC.

Then in similar triangles ABC and ACD BC / AC = AC / AD = AB / CD.

AC ^ 2 = BC * AD = 8 * 18 = 144.

AC = 12 cm.

Answer: The length of the AC diagonal is 12 cm.



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