Original: For example, if the angle between the road and the uphill direction, projected onto the horizontal plane, is 60 °, then the steepest slope along the road will be 20%, which is 40% times the cosine of 60 °.
Simplified: For example, if the angle between the road and the uphill direction, projected onto the horizontal plane, is 60 °, then the steepest slope along the road will be 20% which is 40% times the cosine of 60 °.