Tangent/Normal with derivative

[iRaid]

Homework Statement

Find the lines that are (a) tangent and (b) normal to the curve y=x³ at the point (1,1).

Homework Equations

The Attempt at a Solution

So first I found the derivative, 3x². Then I used x=1 to find the slope which is 3.

(a)y-1=3(x-1)
y=3x-2

(b)y-1=(-1/3)(x-1)
y=(-1/3)x+(4/3)Not really sure if I found the slope correctly tho..

 

[SammyS]

It looks good to me.

If two lines are perpendicular, then the product of their slopes is -1 .

 

[QuarkCharmer]

Looks good to me. I see no problem with a or b.

 

[iRaid]

Thanks :p