C++ :: How To Calculate X And Y In Sine Wave

I have the following initial code:

Code:
double objectAngle = -90.0f;
double objectSpeed = 3.0f; // meters per second
double objectDistance = 300.0f;
double objectTime = 0.0f;
double objectHeading = 90.0f;
double elapsedTimePerCycle = 1.0f;

My coordinate system looks like this:

Code:
90 y
|
|
|
+-180 -------------------- 0 x
|
|
|
-90

I want to calculate a new x,y such that it follows a sine wave like pattern until it gets to point (0,0). I want the width of the arc to go out to about -45 degrees, and the same on the other side to about -135 degrees.

How can I compute these new x,y coordinates in C++?