This ppt includes Theorem 7.2 Proof

1. Theorem : Angles opposite to equal sides of an isosceles triangle are
equal.
PROOF-
GIVEN:
In isosceles Triangle ABC,
AB=BC
TO PROVE:∠𝑩 = ∠𝑪
CONSTRUCTION-Let us draw the bisector of ∠ A and let D be the point of
intersection of this bisector of ∠ A and BC
PROOF-In Δ BAD and Δ CAD,
AB = AC (Given)
∠BAD = ∠CAD (By construction)
AD = AD (Common)
So, Δ BAD ≅ Δ CAD (By SAS rule)
So, ∠ABD = ∠ACD, since they are corresponding angles of congruent triangles.
So, ∠B = ∠C