NCERT Class 9 Solutions: Line and Angles (Chapter 6) Exercise 6.2 – Part 3 (For CBSE, ICSE, IAS, NET, NRA 2022)

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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 ₹ 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 ₹ at C and again reflects back along CD. Prove that .

Line of PQ and ₹ It is a Parallel


Draw ray

Two Line PQ and ₹ 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,

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