Let P(k)=(1+cosπ4k)(1+cos(2k+1)π4k)(1+cos(2k−1)π4k)(1+cos(4k−1)π4k) then which of the following is/are correct?
Let P(x) = x6 + ax5 + bx4 + cx3 + dx2 + ex + f be a polynomial such that P(1)=1; P(2)=2; P(3)=3; P(4)=4; P(5)=5; P(6)=6 then find the value of P(7).