Things Flashcards
Centre of mass of a semicircle
4r/3π
Centre of mass of solid cone
1/4 h
Centre of mass of hollow cone
1/3 h
Centre of mass of a solid hemisphere
3/8 r
Centre of mass of a hollow hemisphere
1/2 r
Even function
f(x)=f(-x)
Odd function
f(-x)=-f(x)
I.e. rotational symmetry of 2
d/dx(tan x)
sec^2(x)
d/dx(cosec x)
-cosec x cot x
d/dx(sec x)
sec x tan x
d/dx(cot x)
-cosec^2(x)
S tan x dx
ln(sec x) + c
S cosec x dx
-ln(cosec x + cot x) + c
S sec x dx
ln(sec x + tan x) + c
S cot x dx
ln(sin x) + c
SinCos -+ identities
cos(π-α) = -cos(α) cos(α-π) = -cos(α) cos(-α) = cos(α)
sin(π-α) = sin(α) sin(α-π) = -sin(α) sin(-α) = -sin(α)
Double angle formulae
sin(2A)=2sinA cosA
cos(2A)=cos^2(A)-sin^2(A)
=2cos^2(A) - 1
=1 - 2sin^2(A)
Half angle formulae
Use double angle formulae and replace A with θ/2
PF denominator with linear factor
(ax+b) -> A/(ax+b)
PF denominator with irreducible quadratic factors
(ax2 + bx + c) -> (Ax + B)/(ax2+bx+c)
PF denominator with a repeated factor
(ax+b)^2 -> A/(ax+b) + B/(ax+b)^2
PF improper
When degree of numerator is greater than or equal to degree of numerator, quotient is polynomial of order top - bottom
Order4/order3 -> Ax + B + other fractions from other rules
Integration by parts
S uv’ = uv - S u’v
Integrating odd powers of sinx and cosx
Split sin^3(x) into sinx and sin^2(x), then convert the latter into 1-cos^2(x). Expand brackets and separate integrals.