計(jì)算:(sin54-tan18*cos54)*(1+根號(hào)3*tan24)/sec24以上均為角度,請(qǐng)寫(xiě)出具體過(guò)程p168輔導(dǎo)與訓(xùn)練

熱心網(wǎng)友

原式=(cos36-tan18*sin36)*(1+根號(hào)3*tan24)*cos24 =[cos36-(sin18/cos18)*2*sin18*cos18]* [cos24+根號(hào)3*(sin24/cos24)*cos24] =[cos36-2*(sin18)^2]*[cos24+根號(hào)3*sin24] =[1-2*(sin18)^2-2*（sin18)^2]*{2*[(1/2)*cos24+(根號(hào)3）/2*sin24} =[1-4*(sin18)^2]*[2*(sin30*cos24+cos30*sin24] =[1-4*(sin18)^2]*（2*sin54) =[1-4*(sin18)^2]*[2*sin(3*18)]再求出sin18與cos18的值就可以了。提示：5*18=90