Visual Optical Illusion Test: An optical illusion is a mind-bending illustration of an object or drawing or picture that has different appearances if looked at from different perspectives. There are ...

Horizontal lines run left to right, parallel to the horizon, with slope 0 and equation y = k. Vertical lines run top to bottom, perpendicular to the horizon, with undefined slope and equation x = k.

In order to work with gradients and straight lines successfully, a good understanding of coordinates and linear graphs is needed. The gradient of a line is calculated by dividing the difference in the ...