Proved that sum of interal angle is 180

1.	Proved that sum of interal angle is 180
Answer» Given . Abc is a triangleTo prove .angle1+"2+"3=180Proof.AB\|\|DEAngle1+angle2+angle3=1801=5(alt..ang.)3=4(alt..ang)Added angle2 both sides1+2+3=5+2+4=1801+2+3=1805+2+4=180Proved

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