Question

Find the equation of the tangent to the curve y= 4x-tanx at the point where x=pi/4. I tried finding the first derivative and then plugging in values but even my slope is wrong.

Answer 1

you need the first derivative for the slope, not the second

Answer 2

sorry i meant first derivative.

Answer 3

did you get\[y'=4-\sec^2(x)\]?

Answer 4

yes. then i turned it into y'= 4- cosx/sinx and plugged in pi/4

Answer 5

that is your mistake

Answer 6

\[\sec^2(x)=\frac{1}{\cos^2(x)}\]

Answer 7

you were thinking of cotangent , not cosecant

Answer 8

now it should work out, right?

Answer 9

OMG silly error. aha yeah , thanks!

Answer 10

yw