Q123 of 158 Page 159

If the sides of a triangle are produced in an order, show that the sum of the exterior angles so formed is 360°.

Formula Used/Theory:-


Angle sum property


Sum of all angles of triangle is 180°


Exterior angle is equal to sum of interior opposite angles


Let 3 angle of triangle be x;y;z


Exterior angle opposite of x will be y + z


Exterior angle opposite of y will be x + z


Exterior angle opposite of z will be x + y


sum of all 3 exterior angles will be


(y + z) + (x + z) + (x + y)


= 2x + 2y + 2z


= 2(x + y + z)


By angle sum property of triangle


x + y + z = 180°


sum of exterior angles is 2(x + y + z)


= 2× 180° = 360°


Result:- sum of exterior angles is 360°


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