Question

1) sin (290+a)-cos (340-a)/sin (110+a)=-2 
2) sina/sina-cosa*tga/2 
3) 1+cosa+cos2a+cos3a/cosa+2cos^2a-1

Answer 1

1)1) sin (290+a)-cos (340-a)/sin (110+a)=-2
sin(110+a)-cos(20+a)/sin(90+(20+a))=cos(20+a)-cos(20+a)/cos(20+a)=cos(20+a)-1=-2
cos)20+a)=-1
20+a=180+360*k
a=160+360*k
3) 2cos^2a+2cosacos2a/(cosa+cos2a)=2cosa(cosa+cos2a)/(cosa+cos2a)=2cosa