Write the principal value of

7

If write the value of x.

8

Simplify:

10

Let * be a ‘binary’ operation on N given by a*b = LCM (a, b) for all a, b ÎN. Find 5 * 7.

11

If (cos x)^y = (cos y)^x, find

OR

If sin y = x sin(a + y), prove that