why sine and cos functions can be used interchangebly in wave motion?

A particle on a speing executes shm when the particle is found at x=xmax/2 the speed of the partcle is 

A)vx=vmax 

B)vx=√3vmax/2

C)vx=√2vmax/2

D)vx=vmax/2

displacement associated with three dimensional wave is given by sai x y is equal to 1 + 1 by 2 x + root 3 by 2 k x minus omega t show that the wave propagates along a direction making an angle 60 degree with the x-axis

What do you mean by Energy of Simple Hormonic Motion?

 

What is mean by motion and time define it's all types with there parts and their s.i. units.

explain the effects of doppler effect in satellite communication