Math 2270 Exam 1 Formulas

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50 Terms

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v/||v||

Unit Vector

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√(x² + y² + z²)

Magnitude

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<a+x, b+y, c+z>

v + w

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<a-x, b-y, c-z>

v - w

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ax + by + cz

v · w Dot Product

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||v||²

v · v

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||v||||w||cos(θ)

v · w angle

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 w((v · w)/(||w||²))

projw(v)

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 v((v · w)/(||v||²))

projv(w)

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i j k

v1 v2 v3

w1 w2 w3

v × w cross product

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||v||||w||sin(θ)

||v × w||

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u · (v × w)

Area of a Parallelapiped

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x(t) = x0 + ta,
y(t) = y0 + tb,
z(t) = z0 + tc

Parametric Equations

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t = (x-x0)/a = (y-y0)/b = (z-z0)/c

Symmetric Equations

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(||v × AC||)/||v||

Distance of a point to a line

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|n ·  AC| / ||n||

Distance of a point to a plane

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A vector orthogonal to the plane

ax + by + cz: <a,b,c>
OR
u × v

Normal Vector

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Normal Vector: <a,b,c>
Point: (x0,y0,z0)

a(x-x0) + b(y-y0) + c(z-z0) = 0

Plane Equation

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x = rcos(θ)

Polar Coordinates: x =

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y = rsin(θ)

Polar Coordinates: y =

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r² = x² + y²
r = √(x²+y²)

Polar Coordinates: r =

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tan(θ) = y/x
θ = arctan(y/x)

Polar Coordinates: θ =

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r = Ρsinφ

Spherical Coordinates: r =

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x = rcosθ = Ρsinφcosθ

Spherical Coordinates: x =

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y = rsinθ = Ρsinφsinθ

Spherical Coordinates: y =

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z = Ρcosφ

Spherical Coordinates: z =

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Ρ = √(x²+y²+z²)

Spherical Coordinates: Ρ =

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φ = arccos(z/P)

Spherical Coordinates: φ =

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θ = arctan(y/x)

Spherical Coordinates: θ =

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s(t) = ∫(0,t)||v(u)||du

Arc Length

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||v(t)|| (parameterized)

Speed

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v(t)/||v(t)|| (parameterized)

Unit Tangent Vector

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rx = <1,0,δf/δx(a,b)>

rx =

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ry = <0,1,δf/δy(a,b)>

ry =

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r = rx × ry = <-δf/δx(a,b),-δf/δy(a,b),1>

r =

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<x-a, y-b, z-f(a,b)> · <-δf/δx(a,b),-δf/δy(a,b),1>

Tangent Plane

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f(a,b) + δf/δx(a,b)(x-a) + δf/δy(a,b)(y-b)

Tangent Plane: z =

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df/dt = (δf/δx * dx/dt) + (δf/δy * dy/dt) + (δf/δz * dz/dt) +

df/dt =

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⛛f(x,y) = <δf/δx(x,y), δf/δy(x,y)>

Gradient ⛛f(x,y) =

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Df(a,b)v = v/||v|| · ⛛f(x,y)

Directional Derivative Df(a,b)v Gradient

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(1/||v||)Df(a,b)v

Directional Derivative Df(a,b)(v/||v||)

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⛛f(x,y) = 0, solve for x,y,z.

Critical Points

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⛛f(a,b)

Normal Vector at a Point (a,b)

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| δ²f/δx²(a,b) δ²f/δxδy(a,b) |
| δ²f/δyδx(a,b) δ²f/δy²(a,b) |

det(H(a,b)(f)) = δ²f/δx²(a,b) * δ²f/δy²(a,b) - (δ²f/δxδy(a,b))²

Hessian Matrix

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Local Min

Hessian: Det(H(a,b)(f)) > 0 & δ²f/δx²(a,b) > 0

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Local Max

Hessian: Det(H(a,b)(f)) > 0 & δ²f/δx²(a,b) < 0

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Saddle Point

Hessian: Det(H(a,b)(f)) < 0

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Inconclusive

Hessian: Det(H(a,b)(f)) = 0

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⛛f(x,y,z) = λ⛛g(x,y,z)

Legrange

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⛛f(x,y,z) = <a,b,c>
a(x-x0) + b(y-y0) + c(z-0)

Tangent Plane at a point