NCERT Class 9 Solutions: Line and Angles (Chapter 6) Exercise 6.2 – Part 3

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Alternate Interior angle

Alternate Interior Angle

Q-5 In the figure, if and find x and y.

The AB Parallel CD Also Angle of X and Y





(Alternate interior angles)

(Angles on the same side of transversal)

Now, (AB is a straight line)

Q-6 In the figure, PQ and RS are two mirrors placed parallel to each other. An incident ray AB strikes the mirror PQ at B, the reflected ray moves along the path BC and strikes the mirror RS at C and again reflects back along CD. Prove that.

Line of PQ and RS It is a Parallel


Draw ray

Two Line PQ and RS at a Parallel


………..equation(1) (Alternate interiror Angle)

………….equation(2) (Angle of incidence Angle of reflection)

…………..equation (3) (Angle of incidence Angle of reflection)

From (1),(2) and (3),we get ………..equation(4)

Adding (1)and(4),we get

But these are alternate interior angle and they are equal. So,