In Complex Numbers today, we showed (directly) that multiplication by a complex number corresponds to scaling by its length and rotating by the angle it makes with the real axis. #MathsToday#ALevelMaths#UKMathsChat#ITeachMaths

Example: (2 + i) (15 + 5i) = 15 (2 + i) + 5i (2 + i) = 15 (2 + i) + 5 (-1 + 2i) So 15 + 5i ends up at 15 lots of 2+i plus 5 lots of -1+2i, and we observed (using Geogebra) that -1+2i was what you get by rotating 2+i by a right-angle. But 15 + 5i starts out as 15 lots of 1 plus 5 lots of i.