已知a角的终边经过p(4/5,3/5)求sina的值2.sin（π/2-a）/sin(a-π）乘以tan(a-π)/cos(3π-a)的值.

已知a角的终边经过p(4/5,3/5)求sina的值2.sin（π/2-a）/sin(a-π）乘以tan(a-π)/cos(3π-a)的值.
已知a角的终边经过p(4/5,3/5)求sina的值
2.sin（π/2-a）/sin(a-π）乘以tan(a-π)/cos(3π-a)的值.

已知a角的终边经过p(4/5,3/5)求sina的值2.sin（π/2-a）/sin(a-π）乘以tan(a-π)/cos(3π-a)的值.
r=1.sina=y/r=3/5
sin（π/2-a）/sin(a-π）乘以tan(a-π)/cos(3π-a)的
=cosa/-sina*tana/-cosa
=tana/sina
=sina/cosa*sina
=sin^2a/cosa