In a ΔABC, AB = AC = 20 cm. D, E, F are the midpoints of sides AB, AC and BC respectively. Find the ratio of area of quadrilateral ADFE to the area of ΔABC.
AD = BD = 10
ABC is isosceles triangle. Median is same as perpendicular bisector. So ∠AFC = ∠AFB = 90∘
BC is tangent to the circle; AF is perpendicular so AF must be the diameter. (Radius is perpendicular to tangent)
So ∠ADF and ∠AEF = 90∘.
So, ADEF is a square.
Area of quadrilateral ADEF = 100
Area of triangle ABC = 200
So the required ratio is 1:2.