FP1 - Further Pure 1
1Complex Numbers
z = a + bi with i^2 = -1. Real part \Re(z) = a, imaginary part \Im(z) = b. Complex conjugate \bar{z} = a - bi. Modulus |z| = \sqrt{a^2+b^2}; argument \arg z = \tan^{-1}(b/a), range -\pi < \arg z \le \pi.
Arithmetic: add componentwise; multiply as (a+bi)(c+di) = (ac-bd) + (ad+bc)i; divide by multiplying by conjugate of denominator. z \times \bar{z} = a^2 + b^2.
Polar & Euler form
Modulus & argument rules
Trigonometric identities via complex numbers
Used to expand powers of \sin/\cos for integration.
Argand Diagram Loci
- Circle: |z - z_1| = r -> Cartesian: (x-a)^2 + (y-b)^2 = r^2
- Perpendicular bisector: |z - z_1| = |z - z_2|
- Half-line: \arg(z - z_1) = \theta
- Max/min modulus on circle: max |z| = |centre| + radius; min = |centre| − radius
2Roots of Quadratic Equations
If \alpha, \beta are roots of ax^2 + bx + c = 0: \alpha + \beta = -\dfrac{b}{a}, \alpha\beta = \dfrac{c}{a}.
Common root identities
Given transformed roots (e.g. \alpha^2, \beta^2 or \tfrac{1}{\alpha}, \tfrac{1}{\beta}), compute their sum and product and reconstruct the new quadratic: x^2 - (\text{sum})x + (\text{product}) = 0.
Common transformations
| New roots | Sum | Product |
|---|---|---|
| \alpha^2, \beta^2 | (\alpha+\beta)^2 - 2\alpha\beta | (\alpha\beta)^2 |
| \frac{1}{\alpha}, \frac{1}{\beta} | \frac{\alpha+\beta}{\alpha\beta} | \frac{1}{\alpha\beta} |
| \alpha^2\beta, \alpha\beta^2 | \alpha\beta(\alpha+\beta) | (\alpha\beta)^3 |
3Numerical Solutions
Change of sign
If f continuous and f(a) \cdot f(b) < 0, a root lies in (a, b).
Interval bisection
Take midpoint of interval, discard half with same sign as bound, narrow interval repeatedly.
Linear interpolation
Newton-Raphson
Fast convergence for locating roots. Fails if f'(x_n) = 0.
4Coordinate Systems
Parabola
Standard form y^2 = 4ax: focus (a, 0), directrix x = -a.
Tangent at point t: ty = x + at^2. Normal at point t: y = -tx + 2at + at^3.
Chord joining t_1 and t_2: y(t_1 + t_2) = 2x + 2at_1 t_2.
Rectangular hyperbola
Standard form xy = c^2. Parametric form: x = ct, y = c/t.
Tangent at point t: x + t^2 y = 2ct. Normal at point t: t^3 x - ty = c(t^4 - 1).
5Matrix Algebra
Matrix multiplication: column count of first = row count of second. Associative but not commutative: (AB)C = A(BC); usually AB \ne BA.
Singular matrix (\det = 0): no inverse exists. Solve linear simultaneous equations: form AX = B, solution X = A^{-1}B.
6Transformations
The columns of a 2 \times 2 matrix are the images of \binom{1}{0} and \binom{0}{1}. Area scale factor = |\det(M)|.
Combined transformations: apply right matrix first, left matrix second. Composition = matrix multiplication in reverse order.
7Series (Sums of Powers)
Use these with linearity: \sum (ar^2 + br + c) = a\sum r^2 + b\sum r + cn.
Method of differences (telescoping series)
8Proof by Induction
Step 1 - Base case: verify statement holds for n = 1 (or smallest relevant integer).
Step 2 - Assumption: assume true for n = k.
Step 3 - Inductive step: prove statement holds for n = k+1 using the assumption.
Step 4 - Conclusion: since base holds and the step is valid, statement true for all positive integers n.
Common proof types: sum series, divisibility, matrix powers, recurrence relations.