rstudio legend

sequencea <- seq(0,6.28,by = pi/8)

plot(sin(sequencea))
     points(cos(sequencea),col="red",pch =2)
     points(tan(sequencea),col="blue",pch = 3,)
legend("bottomleft",pch = c(1,2,3),legend = c("sin","cosine","tan"),col= c("black","red","blue"))