Assertion: ellipse's form | /r/HasProperty | x 1 − a)x
Facets:
Source sentences:
text: If P = (x 1 , y 1 ) and the circle has centre (a, b) and radius r, then the tangent line is perpendicular to the line from (a, b) to (x 1 , y 1 ), so it has the form (x 1 − a)x