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4.2.4—Straight lines

Syllabus
9709–2028–2029
Objective
4.2.4
Level
A2

A vector line can be tested against a complex locus by substitution

To find where a line meets a locus, parameterise the line, substitute its coordinates into the modulus or argument condition, and solve for permitted parameter values.

Check the parameter interval and retain only points satisfying every original condition. A quadratic parameter may represent two, one or no intersections.

Substituting z=1+iλ into |z|=√2 gives 1+λ²=2, so λ=±1 and two points on the circle.

Solving the squared modulus equation can introduce a sign or domain issue; verify in the unsquared condition.

ConceptA-Level CAIE Mathematics A2