How many 1's are there in the base 3 expansion of the following expression?
This section requires Javascript.
You are seeing this because something didn't load right. We suggest you, (a) try
refreshing the page, (b) enabling javascript if it is disabled on your browser and,
finally, (c)
loading the
non-javascript version of this page
. We're sorry about the hassle.
Proof sketch
All we need to do is determine the coefficient of the x 2 0 1 6 term in 4 cos 3 ( x ) , the rest isn't imporant because after taking the 2 0 1 6 t h derivative and plugging in x = 0 all others terms will disappear.
We know 4 cos 3 ( x ) = cos ( 3 x ) + 3 cos ( x ) .
Therefore the x 2 0 1 6 term will be: 2 0 1 6 ! 3 2 0 1 6 + 3 x 2 0 1 6
∴ d x 2 0 1 6 d 2 0 1 6 4 cos 3 x ∣ ∣ ∣ ∣ x = 0 = 3 2 0 1 6 + 3
In base 3 this is obviously 1 0 0 . . . 0 1 0 consisting of only 2 1 ′ s