Sir, How Can We Determine The Value Of Theta When Representing In Polar Form ?

Okay, so now, if you have 

 

cos(theta) = 1/2, sin(theta) = root(3)/2

 

Remember you trignometric tables and see for what value of theta is this true i..e cos(theta) = 1/2, sin(theta) = root(3)/2. 

 

You will realize that with cos60 = 1/2 and sin 60 = root(3/2)

and hence, if you will compare it back to the given equations you are trying to solve, 

the theta = 60 degree.