is equal to 

• 4

• 3

• 2

• 1/2

A particle is projected from a point O with velocity u at an angle of 60^o with the horizontal. When it is moving in a direction at right angles to its direction at O, its velocity then is given by

• u/3

• u/2

• 2u/3

• 

D.

u cos 60^o = v cos 30^o

A value of θ for which  is purely imaginary is

• π/3

• π/6

• 
• 

D.

Let z =  is purely imaginary. Then, we have Re (z) = 0
We have Re (z) = 0
Now, consider z = 

Consider f(x) = tan^-1 . A normal to y = f (x) at x = π/6 also passes through the point

• (0,0)

• (0, 2π/3)

• (π/6 ,0)

• (π/4, 0)

B.

(0, 2π/3)

If 0≤x<2π, then the number of real values of x, which satisfy the equation cosx+cos2x+cos3x+cos4x=0, is :

• 3

• 5

• 7

• 9