How can I find the angle for a combined SHM graph without using a calculator?

[sadhu]

while doing physics , i just stuck on problem regarding mathematics

i wanted to plot the graph of combined SHM but in the formula there is a big problem regarding finding the angle of the given tangent.

i first used inverse tan but got a very weird wave, later i realized that inverse tan can give solutions between 0 -$$\pi$$ but what i wanted was a continuous increase in angle.
i.e > $$\pi$$or2*$$\pi$$, as angle increases with time(x -axis)

can somebody tell how to find angle

 

[HallsofIvy]

Your calculator is giving the "principal value", specifically that value of t between $-\pi$ and $\pi$. Since tangent is periodic with period $\pi$ your other values will be that number, plus $\pi$, plus $2\pi$, plus $3\pi$, etc.

 

[sadhu]

the problem is that i am not working with a calculator , i am dealing with microsoft math
it can plot a graph once you have given the function to it. so nothing can be done manually , i just wanted an expression which works