In the following figure; AB is the largest side and BC is the smallest side of triangle ABC. Write the angles x0, y0 and z0 in ascending order of their values.
This means, the angles opposite to the sides will also have the same relation.
=>∠ACB>∠ABC>∠BAC -- (1)
Since, xo,yo,zo are the exterior angles, they will be 180o−∠BAC;180o−∠ABC,180o−∠ACB respectively. -- (2)
Hence, from 1,2