# Find the tangent to the curve y=x^2 at point (1,2) by differentiation method.

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### 2 Answers

You need to write the equation of tangent line to the curve, at the point `(1,2), ` such that:

`y - 2 = (dy)/(dx)|_(x=1)(x - 1)`

You need to differentiate the given function `y = x^2` with respect to x, such that:

`(dy)/(dx) = 2x`

Evaluating `(dy)/(dx)` at `x = 1` yields:

`(dy)/(dx)|_(x=1) = 2`

Replacing 2 for `(dy)/(dx)|_(x=1)` yields:

`y - 2 = 2(x - 1) => 2x - y - 2 + 2 = 0 => y = 2x`

**Hence, evaluating the equation of tangent line to the given curve, at `(1,2)` , using differentiation method, yields **`y = 2x.`

### User Comments

`y=x^2` `y'=2x` `y'(1)=2`

So:

`y-2=2(x-1)` `y=2x`

Notethe point `P(1;2) ` doesn't lay on parabolas