# Perpendicular lines

`M_a\times\M_b=-1`

Two lines are perpendicular if you multiply the gradients of the two lines together and the

result is -1.

To remember this formula work out what the slopes of an X would be.

`Gradient (m) =y/x`

`Gradient\ of\ li\n\e\ A=1/1=1`

`Gradient\ of\ li\n\e\ B=1/-1=-1`

This shows when we multiply them together `1\times-1 = -1`

Therefore `M_a\timesM_b=-1`

# Perpendicular lines

`M_a\times\M_b=-1`

Two lines are perpendicular if you multiply the gradients of the two lines together and the

result is -1.

To remember this formula work out what the slopes of an X would be.

`Gradient (m) =y/x`

`Gradient\ of\ li\n\e\ A=1/1-1`

`Gradient\ of\ li\n\e\ B=1/-1-1`

This shows the connection between lines with gradients 1 and -1.

When we multiply them together `1\times-1 = -1`

Therefore `M_a\timesM_b=-1`