Points, Lines & Tangents

Revision

Points in a 2D plane are of the form $(a,b)$ where $a$ is the $x$ coordinate and $b$ is the $y$ coordinate.

Straight lines can have either of the following equations:

$y = mx + c$

$y - b = m(x - a)$

One requires knowing the y-intercept and the other simply any point along the line.

Tangents

This can also be used for problems involving tangents where $(a,b)$ are the $x$ and $y$ coordinates of the point the tangent meets the line of the function. The gradient $m$ is also given by $f'(a)$.

Example in one of the past papers.