Question

已知角a的终边过点P (a,-2a)(a不=0),求tanA,sinA+cosA

Answer 1

sinA=-2a/√(a^2+4a^2)=-2a/|a|√5=±2√5/5

cosA=±√1-(sina)^2=±√(1-4/5)=±√5/5

当a>0时,点P在第四象限,所以sinA0,所以tanA=sinA/cosA=(-2√5/5)/(√5/5)=-2,sinA+cosA=-2√5/5+√5/5=-√5/5

当a0,cosA