Question

I WILL AWARD BRAINLIEST!! PLEASE HELP!!

Given: AC = AB, CD = DE
m∠ABC = 70°, m∠ ECB = 35°

Prove: DE ║BC


m∠ACB = m∠______, By reason ( Base angles theorem, Exterior Angle theorem, Supplementary angles, Vertical Angles theorem ) - choose one

Answer 1

Step-by-step explanation:

Well we know that ∠ACB≅∠ABC because ΔABC is isosceles, so base angles theorem applies.

m∠ACB=70°

So m∠DCE=m∠DEC=35° because of base angles theorem, and because m∠DCE=m∠ACB-m∠ECB=70°-35°

Finally, DE║CB because the alternate interior angles ∠ECB≅∠DEC