Question

the sum of any two side off triangle is then the third side is​

Answer 1

Step-by-step explanation:

Let ABC be a triangle,  

We can extend BA past A into a straight line,

Then there is a point D such that DA=CA

Therefore, from Isosceles triangle has two equal angles,

∠ADC=∠ACD

Thus, in △DCB,  

∠BCD>∠BDC (Side opposite greater angle is larger)

Thus, BD>CD

BA+AD>CD (Since, AC=AD)

BA+AC>CD