Докажите тождество : sin/ (1-cost)=(1+cost)/sin t

sin/ (1-cost)=(1+cost)/sin t;
sin t/ (1-cos t)-(1+cos t)/sin t= (sin²t-(1-cos²t))/((1-cos t)sin t)=(sin²t-1+cos²t)/((1-cos t)sin t)=(1-1)/((1-cos t)sin t)=0.