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Why does adding a constant to a function not change its derivative?

Adding a constant to a function does not change its derivative because the derivative of a constant is zero. When differentiating a sum, the constant term vanishes, leaving the derivative of the original function unchanged.

Conditions

  • The function is differentiable.
  • The added term is a constant (e.g., 1, π\pi, or CC).

Reasoning, step by step

  1. Start with a base function, such as x2x^2.
  2. Add a constant to the function, resulting in x2+Cx^2 + C.
  3. Apply the differentiation operator ddx\frac{d}{dx} to the new function.
  4. Observe that the derivative of the constant CC is 0.
  5. Conclude that ddx[x2+C]=2x+0=2x\frac{d}{dx}[x^2 + C] = 2x + 0 = 2x.

Example

The video demonstrates this by showing that ddx[x2]=2x\frac{d}{dx}[x^2]=2x, ddx[x2+1]=2x\frac{d}{dx}[x^2+1]=2x, and ddx[x2+π]=2x\frac{d}{dx}[x^2+\pi]=2x. The mathematical point is that constant terms vanish under differentiation, so the derivative stays fixed even though the original functions change.

Common misconceptions

  • Believing that adding a constant shifts the derivative by the same amount.
  • Thinking that the derivative depends on the vertical position of the graph rather than its slope.

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Answers are generated from source material and independently checked. Consult the original video or creator if something is unclear.