prove that Σ_(k=0) ^(k=n) cos^2 (kx)= ((n+1)/2) + ((sin((n+1)x)cos(nx))/(2 sinx))
x from R−{ kπ.kεZ}then find the value of integral
∫_0 ^π ((sin((n+1)x)cos(nx))/(sinx))dx
I think of a two digit number.The sum of the digits is 9.
When the number is reversed and subtracted from the
original, the result is 45. Find the original number