Question

For what values of x does the graph of f have a horizontal tangent? (Use n as your integer variable. Enter your answers as a comma-separated list.)
f(x) = x − 2 sin x

Answer 1

solve f'(x) = 0

Answer 2

f'(x) + cos(x) = 0 ?

Answer 3

I have ten minutes could someone give me a clear answer?

Answer 4

f'(x) = 1 - 2 cos x

Answer 5

1 - 2 cos x = 0
cos x = 1/2

Answer 6

is the answer 0, 1/2 then?

Answer 7

no

Answer 8

use unit circle http://www.sciencedigest.org/UnitCircle.gif

Answer 9

:(

Answer 10

the answer is Pi/3, 5*Pi/3

Answer 11

+ all multiples of 2Pi

Answer 12

cos x = 1/2 means you looks for the angle where the x coordinate is 1/2

Answer 13

so like pi/6?

Answer 14

no that's a solution to sin x = 1/2

Answer 15

I'm really lost. I really need to sleep more. 4 mins to go, feeling generous and just want to throw the full answer out there?

Answer 16

oh, cos is on the left side, sin on the right side. Like i said i need more sleep. heh.

Answer 17

Pi/3 + n*2*Pi and 5*Pi/3 + n*2*Pi, not sure how they want you to enter it

Answer 18

well, I ran out of time, but I appreciate the effort anyway
thanks! here's your medal