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Taylor series of cos(x)

\cos{\left(x \right)}

Step by step

  1. f(x) = \cos{\left(x \right)}

    Taylor series about x = 0: f(x) = Σ fᵏ(x₀)/k! · (x − x₀)ᵏ.

  2. f^{(0)}(0) = \cos{\left(x \right)}\big|_{x=0} = 1

    Derivative 0 at the centre.

  3. f^{(1)}(0) = - \sin{\left(x \right)}\big|_{x=0} = 0

    Derivative 1 at the centre.

  4. f^{(2)}(0) = - \cos{\left(x \right)}\big|_{x=0} = -1

    Derivative 2 at the centre.

  5. f^{(3)}(0) = \sin{\left(x \right)}\big|_{x=0} = 0

    Derivative 3 at the centre.

  6. f^{(4)}(0) = \cos{\left(x \right)}\big|_{x=0} = 1

    Derivative 4 at the centre.

  7. f^{(5)}(0) = - \sin{\left(x \right)}\big|_{x=0} = 0

    Derivative 5 at the centre.

  8. \frac{x^{4}}{24} - \frac{x^{2}}{2} + 1

    Assemble the terms up to degree 5.

Reveal the answer
\frac{x^{4}}{24} - \frac{x^{2}}{2} + 1 + O((x-0)^{6})