


Tangents, Derivatives and DifferentiationThe Slope of a LineLet P = (x_{1},y_{1}) and Q =(x_{2},y_{2}) be two points on the Cartesian plane. The slope of the straight line passing through P and Q is
where
and and
we say "the slope is equal to the change in y relative to
the change in x" .
A vertical line has undefined slope because all points on the line have the same xcoordinate . As a result the formula used for slope has a denominator of 0, which makes the slope undefined. Differentiation Index  The Slope of a Tangent Line >> 