∵sinα=1/3,α第二象限∴cosα=-2√2/3
cos(a+pai/3)=cosαcosπ/3-sinαsinπ/3=1/2×1/3+2√2/3×√3/2=1/6+√6/3=(1+2√6)/6sin(a-2pai)*cos(3pai/2-a)+tan(pai-a)*tan(pai/2+a)+cos2(pai/2+a)這題怎么做？一樣的啊原式=(-sinα)×(-sinα)+(-tanα)×(-cotα)+(-cos2α) =sinα×sinα+1-cos2α=(sinα)^2-(cos^α-sin^2α)+1=sinα(sinα+4cosα)=1/3×(1/3+4×(-2√2/3))=(1-8√2)/9