Question

Prove that sum of the angles of a triangle is 180 deg when no angles are given

Answer 1

Let the Angles be 1x, 2x, 3x.
If the sum of the Angles is 180..
Proving ..
1x+2x+3x = 180
6x = 180
x= 180/6
30
Now putting the value,
1x = 1* 30= 30
2x = 2*30 = 60
3x = 3*30= 90
Therefore,
Proving with the value..
30+60+90=180
Proved.

Hope It helps you.

Answer 2

first imagine a triangle
 the exterior angle is equal to the sum of two interior angles opposite to the considered exterior angle
let the angles be x,y and z
the angles opposite to z is x,y
so,x+y=exterior angle of z
i hope you know that sum of interior angle and its exterior angle is 180 as they lie on a straight line
so,x+y+z=180