Trigonometry Formulas

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Questions and Answers

Which of the following is the correct expansion of $\sin(A + B)$?

  • $\cos A \cos B + \sin A \sin B$
  • $\sin A \cos B - \cos A \sin B$
  • $\sin A \cos B + \cos A \sin B$ (correct)
  • $\cos A \cos B - \sin A \sin B$

$\cos(A - B)$ is equivalent to $\cos A \cos B - \sin A \sin B$.

False (B)

What is the formula for $\tan(A + B)$?

$\frac{\tan A + \tan B}{1 - \tan A \tan B}$

The double angle formula for sine is: $\sin 2\theta = 2 \sin \theta \cos$ ______

<p>$\theta$</p> Signup and view all the answers

Match the following trigonometric identities with their expansions:

<p>$\sin(C) + \sin(D)$ = $2 \sin(\frac{C+D}{2}) \cos(\frac{C-D}{2})$ $\cos(C) + \cos(D)$ = $2 \cos(\frac{C+D}{2}) \cos(\frac{C-D}{2})$ $\sin(C) - \sin(D)$ = $2 \cos(\frac{C+D}{2}) \sin(\frac{C-D}{2})$</p> Signup and view all the answers

Which of these is a correct formula for $\cos 2\theta$?

<p>$\cos^2 \theta - \sin^2 \theta$ (D)</p> Signup and view all the answers

$\tan 2\theta = \frac{2 \tan \theta}{1 + \tan^2 \theta}$ is the correct double angle formula for tangent.

<p>False (B)</p> Signup and view all the answers

What is the expression for $1 + \cos 2\theta$ using the double angle formulas?

<p>$2 \cos^2 \theta$</p> Signup and view all the answers

The triple angle formula for $\sin 3\theta$ can be expressed as $3 \sin \theta - 4 \sin^3$ ______

<p>$\theta$</p> Signup and view all the answers

If $f(x) = \tan^{-1}(x)$, what is $f'(x)$?

<p>$\frac{1}{1 + x^2}$ (D)</p> Signup and view all the answers

Flashcards

sin(A+B) = ?

sin(A)cos(B) + cos(A)sin(B)

sin(A-B) = ?

sin(A)cos(B) - cos(A)sin(B)

cos(A+B) = ?

cos(A)cos(B) - sin(A)sin(B)

cos(A-B) = ?

cos(A)cos(B) + sin(A)sin(B)

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tan(A+B) = ?

(tan(A) + tan(B)) / (1 - tan(A)tan(B))

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tan(A-B) = ?

(tan(A) - tan(B)) / (1 + tan(A)tan(B))

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sin(C) + sin(D) = ?

2sin((C+D)/2)cos((C-D)/2)

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sin(C) - sin(D) = ?

2cos((C+D)/2)sin((C-D)/2)

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cos(2θ) = ?

cos²(θ) - sin²(θ) or 2cos²(θ) - 1 or 1 - 2sin²(θ)

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tan(2θ) = ?

(2tan(θ)) / (1 - tan²(θ))

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Study Notes

Addition Formulae

  • sin(A + B) = sinA cosB + cosA sinB
  • sin(A - B) = sinA cosB - cosA sinB
  • cos(A + B) = cosA cosB + (- sinA sinB)
  • cos(A - B) = cosA cosB + sinA sinB
  • tan(A + B) = (tanA + tanB) / (1 - tanA tanB)
  • tan(A - B) = (tanA - tanB) / (1 + tanA tanB)

Factorization Formulae

  • sinC + sinD = 2 sin((C + D)/2) cos((C - D)/2)
  • sinC - sinD = 2 cos((C + D)/2) sin((C - D)/2)
  • cosC + cosD = 2 cos((C + D)/2) cos((C - D)/2)
  • cosC - cosD = -2 sin((C + D)/2) sin((C - D)/2)

Double Angle Formulae

  • sin2θ = 2 sinθ cosθ
  • cos2θ = cos²θ - sin²θ
  • cos2θ = 2 cos²θ - 1
  • cos2θ = 1 - 2 sin²θ
  • tan2θ = (2 tanθ) / (1 - tan²θ)
  • sin2θ = (2 tanθ) / (1 + tan²θ)
  • cos2θ = (1 - tan²θ) / (1 + tan²θ)

Important Formulae

  • 1 + cos2θ = 2 cos²θ
  • 1 - cos2θ = 2 sin²θ

Triple Angle Formulae

  • sin3θ = 3 sinθ - 4 sin³θ
  • cos3θ = 4 cos³θ - 3 cosθ
  • tan3θ = (3 tanθ - tan³θ) / (1 - 3 tan²θ)
  • sin3θ / tan3θ = 3 sinθ - sin³θ
  • cos3θ = cos³θ - cos³θ + 3θi

Half Angle Formulae

  • sin(θ/2) = 2 sin(θ/2) + cos(θ/2)
  • cos(θ/2) = cos²(θ/2) - sin²(θ/2)
  • cos(θ/2) = 2 cos²(θ/2) - 1
  • cos(θ/2) = cos(θ/2) - 1 - 2 sin²(θ/2)
  • tan(θ/2) = (2 tan(θ/2)) / (1 - tan²(θ/2))
  • sinθ = (2 tan(θ/2)) / (1 + tan²(θ/2))
  • cosθ = (1 - tan²(θ/2)) / (1 + tan²(θ/2))
  • 1 + sin²θ = (cosθ + sinθ)²
  • (1 - cosθ) / (1 + cosθ) = tan²(θ/2)
  • (1 + tanθ) / (1 - tanθ) = tan(π/4 + θ)

Inverse Trigonometric Functions

  • sin⁻¹(sinx) = x
  • cos⁻¹(cosx) = x
  • tan⁻¹(tanx) = x
  • sin(sin⁻¹x) = x
  • cos(cos⁻¹x) = x
  • tan(tan⁻¹x) = x
  • sin⁻¹(1/x) = cosec⁻¹(x)
  • tan⁻¹x = 1 / (1 + x²)
  • cot⁻¹x = 1 / (1 + x²)
  • sec⁻¹x = 1/(x √(x²-1))
  • cosec⁻¹x = -1/(x √(x²-1))

Derivatives

  • f(x) = y
  • The derivative of xⁿ is nxⁿ⁻¹
  • The derivative of 1/x is -1/x²
  • The derivative of eˣ is eˣ
  • The derivative of eᵃ⁺ᵇ is eᵃ⁺ᵇ(a)
  • The derivative of log x is 1/x
  • The derivative of logₐx is 1/(x log a)
  • The derivative of aˣ is aˣ log a
  • The derivative of aˣ/(b+c) is (aˣ log a)/(b+c)
  • The derivative of a constant is 0
  • √(x) the derivative is equal to 1/(2√(x))
  • derivative of sinx = cosx
  • derivative of sin(ax+b) = cos(ax+b)a
  • derivative of cosx = -sinx
  • derivative of cos(ax+b) = -sin(ax+b)a
  • derivative of tanx = sec²x
  • derivative of tan(ax+b) = sec²(ax+b)a
  • derivative of cotx = -cosec²x
  • derivative of secx = secxtanx
  • derivative of sec(ax+b) = (sec(ax+b)tan(ax+b))a
  • derivative of cosecx = -cosecxcotx
  • derivative of cosec(ax+b) = (-cosec(ax+b)cot(ax+b))a
  • derivative of sin⁻¹(x) = 1/√(1-x²)

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