Elf Sternberg

For dealing with when the slope is undefined, you have two options: hardcode the values (this is what most people do, even mathematicians), or use a different form of the equation that doesn't lead to undefined values: the generic equation for a straight line is Ax + By = C (similar to how an ellipse is Ax^2 + Bx^2 = C). The slope-intercept is normalizing for B=-1, which makes m be -A/B...B just happens to be zero, here, so you can't do that.