x <- seq(-2*pi, 2*pi, 0.2)

z <- pi*(-2:2)
labels <- paste(-2:2,"π", sep="")
# 绘制正弦曲线
plot(x, sin(x), type="o", pch=4, col=2, ylim=c(-1.5, 1.5), xaxt="n", ann=F)
# 添加余弦点图
points(x, cos(x), pch=8, col=3)

# 添加参考线
abline(h=c(-1, 0,1), lty=2, col=8)
# 设置图形标题和坐标轴标题
title("sin & con", xlab="x", ylab="y",)
axis(1, at=z, labels=labels)
# 添加图例
legend("bottomleft", inset=0.02, c("sin", "cos"), col=c(2, 3), 
       lty=c(1, -1), pch=c(4, 8), bg="gray95", cex=0.9,pt.cex=0.7, 
       seg.len=0.6, text.width=0.3)