Question

1. Prove the following:
   1. Claim: Consider a convex quadrilateral □ABCD. If σ(□ABCD) = 360, then σ(▵ABC) = σ(▵ACD) = 180.

Hint: Use the Split Triangle Theorem and/or the Split Quadrilateral Theorem

(The angle sum of a convex quadrilateral is the sum of the angle sum of the two triangles formed by adding a diagonal.
Recall: The angle sum of quadrilateral □ABCD is σ(□ABCD) = m∠ABC + m∠BCD + m∠CDA + m ∠DAB.)

Answer 1