Assuming is the first-quadrant angle between the two lines, suppose that is the first-quadrant angle between the x-axis and the line y = 0.5. Then,
, and
.
Also, .
Replace with 0.5, then solve for .
Assuming is the first-quadrant angle between the two lines, suppose that is the first-quadrant angle between the x-axis and the line y = 0.5. Then,
, and
.
Also, .
Replace with 0.5, then solve for .