求值Cos pai/17 *cos 2pai/17*cos 4pai/17*cos 8pai/17

题目

求值Cos pai/17 *cos 2pai/17*cos 4pai/17*cos 8pai/17

答案

cos(π/17)cos(2π/17)cos(4π/17)cos(8π/17)=[16sin(π/17)cos(π/17)cos(2π/17)cos(4π/17)cos(8π/17)]/16sin(π/17)=[8sin(2π/17)cos(2π/17)cos(4π/17)cos(8π/17)]/16sin(π/17)=[4sin(4π/17)cos(4π/17)...