Prove that the sum of all angle of triangle is 180

1.	Prove that the sum of all angle of triangle is 180
Answer» Take a triangle ABC . Draw a straight line passing through A and name it as PQ. Now, draw another line parallel to PQ passing though BC and name it as MN . We get figure. Angle PAB=angle ABC. Angle QAC= angle ACB . angle PAB+angle BAC+angle QAC=180° ----- (eq. 1). (reason : consequetive angles) Substitute the angle PAB and angle QAC into (eq.1)Therefore, angle ABC+ angle BAC + angle ACB =180° Sum of three angle in triangle is 180 We angle as x X1+x2+x3=180 Make a parrrlel line from base Angle 1 is in upper side Angle 2 is co interior angleAngle 3 is also co interior Than the sum of line is 180 Hence proved

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