-4π/3 -5π/4 -5π/3 -7π/4 -8π/3 -11π/4 的sin cos tan 值告我

23/4π=7π+2/3π怎么知道7π+2/3π,还有21/8π=2π+5/8π, -4π/3 -5π/4 -5π/3 -7π/4 -8π/3 -11π/4 的sin cos tan 值告我 求值sin25π/6+cos25π/3+tan(-25π/4)+sin(-7π/3)×cos(-13π/6)-sin(-5π/6)×cos(-5π/3) 计算：cos（π/5)+cos（2π/5)+cos(3π/5)+cos(4π/5) 函数y=tan(1/2x-π/3)的一个单调递增区间A、(-π/3,5π/3)B、(π/6,7π/6)C、(-2π/3,4π/3)D、(-π/6,5π/6) sin5π/7>sin4π/7 COS(-3π/5)>COS(-9π/4) COS3π>COS7π/9 哪个正确 cos(α+π/4)=3/5,-3/4π 已知sin(a-π/4)=3/5,π/4 π,π/3,π/4,π/5分别是奇数角还是偶数角? Cos[π/7] + Cos[2 π/7] + Cos[3 π/7] + Cos[4 π/7] + Cos[5 π/7] + Cos[6 π/7] + Cos[7π/7]过程思路 不要只有答案哦 .求值 M=cos17分之πcos17分之2πcos17分之3πcos17分之4πcos17分之5π.求值 M=cos17分之πcos17分之2πcos17分之3πcos17分之4πcos17分之5πcos17分之6πcos17分之7πcos17分之8π 函数 (4 20:28:50)cos^4 (π /8)+cos^4(3π/8)+cos^4(5π/8)+cos^4(7π/8) = 设0≦x≦2π 且√1+sin2x=sinx+cosx,则x的范围【里面的是2乘A[0,π] B[0,3/4π]∪[7/4π,2π] C[π/2,3/4π]∪[5/4π,2π] D[π/4,5/4π] 比较下列各组三角函数值的大小 1）sinπ/3与sinπ/6 2）sin3π/5与sin4π/7 3）cosπ/4与cosπ/3 4）cos比较下列各组三角函数值的大小 1）sinπ/3与sinπ/6 2）sin3π/5与sin4π/7 3）cosπ/4与cosπ/3 4）cos3π/5与cos5π sin2a =3/5 (-3π/4 已知sin(α+π/4)=3/5,π/2 cos(π/4+x)=3/5,17π/12 cos(π/4+α）=3/5,17π