Question

in the figure l parallel to m. if ABC=ABD=40 and A =90 then prove that ∆BCD is isosceles​

Answer 1

ADB = 180 -90 - 40 = 50

DCB = 180 - 80 - 50 = 50

angle B = 40 + 40 = 80

so, triangle BCD is isosceles