n = 1 ∏ 2 0 1 6 cos ( 2 0 1 7 n π )
If the product above is equal to A − B , where A and B are positive integers with A is a prime number, find A + B .
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.
N I C E ! !
simply we can use the identity P = k = 1 ∏ n − 1 cos ( n k π ) = 2 n − 1 sin ( π n / 2 ) now put n = 2 0 1 7 to get P = 2 2 0 1 6 1 So A + B = 2 0 1 8
Problem Loading...
Note Loading...
Set Loading...
x = n = 1 ∏ 2 0 1 6 cos ( 2 0 1 7 n π ) y = n = 1 ∏ 2 0 1 6 sin ( 2 0 1 7 n π ) x . y = n = 1 ∏ 2 0 1 6 sin ( 2 0 1 7 n π ) cos ( 2 0 1 7 n π ) x . y = n = 1 ∏ 2 0 1 6 2 1 sin ( 2 0 1 7 2 n π ) = ( 2 1 ) 2 0 1 6 [ sin ( 2 0 1 7 2 π ) sin ( 2 0 1 7 4 π ) ⋯ sin ( 2 0 1 7 1 4 π ) sin ( 2 0 1 7 1 6 π ) sin ( 2 0 1 7 1 8 π ) ⋯ sin ( 2 0 1 7 4 0 3 2 π ) ] θ + α = 2 π → sin ( θ ) = − sin ( 2 π − α ) x . y = n = 1 ∏ 2 0 1 6 2 1 sin ( 2 0 1 7 2 n π ) = ( 2 1 ) 2 0 1 6 × ( − 1 ) 1 0 0 8 [ n = 1 ∏ 2 0 1 6 sin ( 2 0 1 7 n π ) ] x . y = ( 2 1 ) 2 0 1 6 × ( − 1 ) 1 0 0 8 . y x = ( 2 2 0 1 6 1 ) = ( A B 1 ) A + B = 2 0 1 8