利用和(差)角公式求下列各三角函数的值 (1) sin(-7π/12) (2)cos(-61π/12) (3)tan(35π/12

问题描述:

利用和(差)角公式求下列各三角函数的值 (1) sin(-7π/12) (2)cos(-61π/12) (3)tan(35π/12

sin(-7π/12)= -sin(7π/12)= -sin﹙π/3+π/4﹚= -(sinπ/3cosπ/4+cosπ/3sinπ/4)= -(√3/2 * √2/2 + 1/2 * √2/2)= -(√6+√2)/4cos(-61π/12)= cos(61π/12)= cos(5π+π/12)= cos(π+π/12)= -cos(π/12)= -...