The exact value of `"cos"(3pi)/(4)` is

The exact value of cos((2 pi)/(28))cos ec((3 pi)/(28))+cos((6 pi)/(28))cos ec((9 pi)/(28))+cos((18 pi)/(28))cos ec((27 pi)/(28))

The exact value of cos((2pi)/28)cosec((3pi)/28)+cos((6pi)/28)cosec((9pi)/28)+cos((18pi)/28)cosec((27pi)/28)

Let the exact value of cos((pi)/(7))+cos^(2)((pi)/(7))-2cos^(3)((pi)/(7)) is a rational number in the form (p)/(q), where p and q are integers.Find (p+q)

The value of cos^(-1)("cos"(3pi)/2) is _____

The value of cos^(-1)(cos'(3pi)/(2)) is