Posted by **James** on Sunday, November 14, 2010 at 11:48pm.

Find all relative extrema and points of inflection of the function:

f(x) = sin (x/2)

0 =< x =< 4pi

=< is supposed to be less than or equal to.

I can find the extrema, but the points of inflection has me stumped. The inflection point is (2pi,0) but shouldn't there be inflection points on x=0 and x=4pi as well?

- calculus -
**Reiny**, Monday, November 15, 2010 at 8:59am
The basic sine curve has points of inflection at every x-intercept of the curve,

y' = (1/2) cos x/2

y' = -(1/4) sin x/2

-(1/4)sin x/2 = 0

gives me x/2 = 0 or x/2 = π or x/2 = 2π etc

or

x = 0 or x = 2π or x = 4π etc

then if you domain is 0 ≤ x ≤ 4π

you are correct, there should have been points of inflection at

(0,0), (2π,0) and (4π,0)

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