if the sides of a triangle are produced in order, prove that the sum of the exterior angles so formed is equal to four right angles​

In the figure, by exterior angle property, you have

ACD = A+ B

CBF = A+ C

BAE = B+ C

Adding the above equations, you get

ACD +CBF +BAE = A+ B +A+ C + B+ C

                                           = 2 (A+ B +C)

                                           = 2 180o      (angle sum of a )

ACD +CBF +BAE =360o

That is the sum of the exterior angles = four right angles. (360o = 490o)

Step-by-step explanation: