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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

circle area = pi * radius^2

if diameter = 10 then radius = 5

circle area = pi * 5^2

circle area = pi * 25

circle area = 78.5398163397 square units

step-by-step explanation: