Mathematics for JEE Main and Advanced

Complex Numbers

Complex numbers drawn on the Argand plane: modulus, argument, rotation and locus, one idea per lesson.

Lesson 1

Modulus and Argument of a Complex Number

A complex number is a point, and also an arrow from the origin. Its modulus is how long the arrow is. Its argument is which way the arrow points.

Coming on Sunday, 11 October at 5 PM IST

The video and its free notes come out together.

Lesson 2

Multiplication of Complex Numbers as Rotation

Multiplying by a complex number w turns the arrow by arg w and scales its length by |w|. The lengths multiply and the angles add, so one multiplication can rotate any point about the origin.

Coming on Wednesday, 14 October at 5 PM IST

The video and its free notes come out together.

Lesson 3

Rotation Theorem in Complex Numbers

To rotate a point about any centre, shift the centre to the origin, turn by multiplying, and shift back. On a triangle, the same idea gives the rotation theorem.

Coming on Sunday, 18 October at 5 PM IST

The video and its free notes come out together.

More lessons are on the way

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