(sin 8-sin 12+sin16)/(cos 8-cos 12+cos 16)=tg12 помогите, СРОЧНО

(sin 8-sin 12+sin16)/(cos 8-cos 12+cos 16)=tg12. (тождество) ------------ (sin 8-sin 12+sin16)/(cos 8-cos 12+cos 16) = ( (sin16+sin8) -sin 12) )/( (cos 16+cos 8) -cos 12) = ( 2sin (16+8)/2 *cos(16-8)/2-sin 12 ) /(2cos(16+8)/2*cos(16 -8)/2-cos12)= ( 2sin 12 *cos4 - sin 12 ) /(2cos12*cos4 -cos12)=  2sin 12(cos4 - 1) /(2cos12(cos4 -1) =tg12.