0xy1-1Π/2Π3Π/22Πy=sinxx∈[0,2π]y=sinx的图象与y=cosx的图象之间的关系y=cosx=cos(-x)=sin[π/2-(-x)]=sin(π/2+x)所以，余弦函数的图象可以通过将正弦曲线向左平移π/2个单位长度而得到。0xy1-1Π/2Π3Π/22Π-Π/2y=sinxx∈[0,2π]y=cosxx∈[-π/2,3π/2]0xy1-1Π/2Π3Π/22Π-Π/2y=cosxx∈[0,2π]yxoπ2π3π4π-π-2π-3π-4π1-1xy1-1oπ2π3π4π-π-2π-3π-4πy=cosx(x∈R)y=sinx(x∈R)yxoπ2π3π4π-π-2π-3π-4π1-1xy1-1oπ2π3π4π-π-2π-3π-4πy=cosx(x∈R)y=sinx(x∈R)小结：1）图象R[-1,1]奇函数偶函数2）性质（KZ)定义域值域奇偶性周期性单调性y=sinxy=cosx周期为2Kπ，最小正周期为2π[-π/2+2Kπ,π/2+2Kπ]增[π/2+2Kπ,3π/2+2Kπ]减[（2K-1）π,2Kπ](k∈z)增[2Kπ,（2K+1）π](k∈z)减
