Why are sine functions used in some of the equations in physics?

For example,in the expression for instantaneous emf induced in a rotating conductor placed in an uniform magnetic field which is given by

E=B*L*V*sin(theta)

where,

B is the strength of the magnetic field,L is the length of the conductor and (theta) is the angle between the direction of motion of the conductor and the magnetic field,and here,my question is why do we use sine function in this expression?what is its need?

Answer:

The function sin (theta) in a right angled triangle = opp. side /Hypotenuse

When we have to take a component perpendicular to another, we take the sine function.

(the answer will be updated with more information soosn)