Paper 1 · Complex Numbers Lesson 1 of 7

LCOL Complex Numbers 1: Introduction to i

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You’ll learn

  • I = √(-1), and squaring both sides gives the rule you use everywhere:…
  • To simplify the square root of a negative, split off √(-1): e.g. √(-9)…
  • A complex number looks like a + bi: a is the real part…

Formula used

i² = −1

On page 20 of the log tables — read it off, don’t memorise.

Most recent exam questions

  • 2026 P1 Q4(b)

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