# Given is an isosceles trapezoid with a large base AD. Calculate the perimeter of the trapezoid if AD = 18 cm

October 6, 2021 | education

| **Given is an isosceles trapezoid with a large base AD. Calculate the perimeter of the trapezoid if AD = 18 cm, BC = 11 cm. AC is the bisector of the angle BAD.**

Since ABCD is a trapezoid, then BC is parallel to AD, and then the angle BCA = CAD as criss-crossing angles at the intersection of parallel straight lines BC and AD secant AC.

AC is the diagonal and the bisector, then the angle BAC = DAC, and then the angle BAC = BCA, and therefore the triangle ABC is isosceles, AB = BC = 11 cm.

Since the trapezoid is isosceles, then CD = AB = 11 cm.

The perimeter of the trapezoid is: Ravsd = AB + BC + CD + AD = 11 + 11 + 11 + 18 = 51 cm.

Answer: The perimeter of the trapezoid is 51 cm.

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