can(sinx)+sinx+sosx+can(sosx)=1
can(sinx)+can(sosx)+sinx+sosx=1
ta binh phuong 2 ve
sinx+sosx+sin^2x+sos^2x=1
(sinx+sosx)+(sin^2x+sos^2x)=1
theo cong thuc thi (sin^2x+sos^2x)=1 nen
(sinx+sosx)+1=1
sinx+sosx=0
chia ca hai ve cho sosx ta duoc
tanx=-1
ta co x=kpi