You should know that the gradient makes the line make an angle with the positive x axis, such that . So from this line we can see
You should also know that if you have two lines and know the angles they make with the positive x axis, then the angle between them can be evaluated by .
You have , you have . Can you evaluate and use this to find the gradient of the line you are trying to find the equation of? From there can you find the equation of the line?