Question

1-cosa+cos2a/sina-sin2a

Answer 1

$dfrac{1-cosa-cos2a}{sina-sin2a}=dfrac{1-cosa-2cos^2a+1}{sina(1-cosa)}=\boxed{left{{{-2cos^2a-cosa+2=0}atop{sina(1-cosa)ne0}} right. }\1)sina(1-cosa)ne0\sinane0 our cosane1\anepi k,kin Z;ane pi k,kin Z\ \2)2cos^2a+cosa-2=0\mathbf{cosalpha=a,ale1}\2a^2+a-2=0\D=1-4*2*(-2)=17\a_1=dfrac{-1+sqrt{17}}{2*2}=dfrac{sqrt{17}-1}{4}\a_2= dfrac{-1-sqrt{17}}{2*2}=-dfrac{sqrt{17}+1}{4}-ne yd. ysl.\cosa=dfrac{sqrt{17}-1}{4}\a=pm arccos(dfrac{sqrt{17}-1}{4})+2pi k,kin Z$