Let us take two angles, say \(60°\) and \(70°\), whose sum is less than \(180°\).
 
Let the included side be \(5 \ cm\).
 
What could the measure of the third angle be? Does this measure change if the base length is changed to some other value, say \(7 \ cm\)? Construct and find out.
 
Construction:
 
Step - 1: Draw a base \(AB\).
 
Step - 2: Through \(A\) and \(B\) constuct angles and respectively, by drawing the other arms of the angle.
 
Step - 3: The of the two arms is the third vertex \(C\).
 
Interpretation:
 
The value of the third angle \(C\) is \(^{\circ}\).
 
Does the change of base length to \(7 \ cm\) change the measure of angle \(C\)?