Answer/Step-by-step explanation:
The figure given shows two triangles.: ∆ADB has two equal base angles while ∆BCD has three equal angles. Therefore, based on their angles, we can conclude that:
∆ADB is an isosceles triangle
∆BCD is an equilateral triangle
Before we add up he outside lengths of Quadrilateral ABCD to find the perimeter, let's recall three properties of each triangle:
Isosceles triangle:
-Has two equal base angles
-The two sides opposite the two equal base angles are also equal to each other
-the their side (base) is unequal to the other
Equilateral triangle:
-Has three equal angles
-Has three equal sides
-Each angle measures 60°
Using these properties, we can determine the outside lengths of quadrilateral ABCD:
AB = 21 (given)
AD = 17 (given)
AD = BD = 17 (equal sides of ∆ADB)
BD = 17
BD = BC = CD = 17 (properties of equilateral triangle)
BC = 17
CD = 17
✔️Perimeter of Quadrilateral ABCD = AB + BC + CD + AD = 21 + 17 + 17 + 17
Perimeter = 72 units
