NCERT Class 9 Solutions: Triangles (Chapter 7) Exercise 7.2 – Part 4
Interior Angle
When two lines are cut by a third line (transversal), then the angles formed inside the lines are called Interior Angles.
Q7 ABC is a right angled triangle in which and . Find and
Solution:
Given, and

Now, (Angles opposite to the equal sides are equal.)

Now, (Sum of the interior angles of the triangle.) (

Thus,
Q8 Show that the angles of an equilateral triangle are each.
Solution:
Give, ABC be an equilateral triangle. (Length of all sides is same) (Sides opposite to the equal angles are equal.)

Also, (Sum of the angles of the triangle.) ( )

Therefore,

Thus, the angles of an equilateral triangle are each.