Question

已知角a的终边上一点P的坐标为(3r,4r)(r≠0),求sina,cosa,tana的值

Answer 1

R=√(x^2+y^2)=√[(3r)^2+(4r)^2]=5|r|

当：r>0时,R=5r

sina=y/R=4r/5r=4/5

cosa=x/R=3r/5r=3/5

tana=y/x=4r/3r=4/3

当：