Further Maths Pure Flashcards
what is the determinant of a 2x2 matrix?
ad-bc
what is the determinant of a 3x3 matrix?
a(ei-fh)-b(di-fg)+c(dh-ge)
what is the formula for volume of revolution around the axes?
around x-axis: π∫y²dx
around y-axis: π∫x²dy
if M is a 2x2 matrix, what is inverse M?
swap a and d
times b and c by -1
times by 1/detM
what is (AB)^-1 equal to?
B^-1 * A^-1
how do you invert a 3x3 matrix?
1: find matrix of minors (determinants of 2x2 matrices when row and column is crossed out)
2: multiply every other number by -1 (the ones in the middle diamond)
3: reflect all values through the leading diagonal (bottom left to top right)
4: multiply by 1/detM
what is consistent/ inconsistent?
consistent is when there is a set of values that satisfies all equations (at least one place where they all cross)
what are invariant lines/points?
lines or points that stay in the same place after a transformation
what is the dot product and cross product formulas for two lines?
a.b=|a| |b| cosθ
axb=|a| |b| sinθ |n̂|
what is the dot product formula for two planes?
n₁.n₂=|n₁| |n₂| cosθ
what is the dot product formula for a line and a plane?
b.n=|b| |n| sinθ
what is r.n̂ equal to?
the shortest distance from the origin to the plane.
what is the vector form of an imaginary number?
r(cosθ+isinθ)
how do you work out the matrix of a rotation around an axis when the matrix is 3x3?
for around x-axis: replace the 2x2 rotation matrix with the numbers that aren’t in the column or row of the x-value (bottom right 2x2)
same for y and z axes
what is the equation of area before and after and determinant?
area before = area after / |determinant|
what is L’Hospital’s Rule and when can it be used?
If lim x→a of f(x) = lim x→a of g(x) = 0 OR ± ∞ THEN
the lim x→a of f(x)/g(x) = lim x→a of f’(x)/g’(x)
how does volumes of revolution work with parametric equations?
V = π∫y² dx/dt dt
V = π∫x² dy/dt dt
with the parameters as a value for t not x or y
how do you find the tangent parallel or perpendicular to the initial line of a polar equation?
parallel: dy/dθ = 0
perpendicular: dx/dθ = 0
must be found by differentiating the equation for y and x after r is substituted out for θ.
what is the equation for sinh and cosh?
cosh(x) = 1/2 (e^x + e^-x) sinh(x) = 1/2 (e^x - e^-x)
how do you solve an equation in the form:
dy/dx + f(x)*y = g(x)
multiply by the integrating factor:
e^( ∫f(x) dx)
the left side will then be in the form left after differentiating by product rule.
integrate both sides and make y the subject.
DONT FORGET THE +C
when a question in core pure has acceleration/ velocity/displacement in an equation, what will the question most likely be asking you to do?
Solving a first or second order differential equation.
what are the two equations that apply to simple harmonic motion?
ẍ = -ω²x where ω is angular velocity
ẍ = v dv/dx
where the dots are order of differential in terms of t
what information can be obtained from the equation:
ẍ + kẋ + ω²x = 0 if the type of damping is known?
heavy damping: k²-4ω² > 0
critical damping: k²-4ω² = 0
light damping: k²-4ω² < 0
what is the area of a triangle and a parallelogram and volume of a tetrahedron and parallelpiped using vectors?
triangle area = 1/2 |axb|
parallelogram area = |axb|
tetrahedron volume = 1/6 |a.(bxc)|
parallelepiped volume = |a.(bxc)|