A,B E(0,180)中E是屬于的符號

熱心網友

asinx+bcosx+c=0 == a*2sin(x/2)cos(x/2)+b*{[cos(x/2)]^2-[sin(x/2)]^2}+c*{[cos(x/2)]^2+[sin(x/2)]^2} = 0== 2a*tg(x/2)+b*{1 -[tg(x/2)]^2}+c*{1+[tg(x/2)]^2} = 0== (c-b)*[tg(x/2)]^2 + 2a*tg(x/2) +(b+c) = 0== tg(A/2)+tg(B/2) = 2a/(b-c), tg(A/2)*tg(B/2) = (b+c)/(c-b)tg(A/2+B/2) = [tg(A/2)+tg(B/2)]/[1-tg(A/2)*tg(B/2)] = a/bsin(A+B)= 2*tg(A/2+B/2)/{1+[tg(A/2+B/2)]^2} = 2ab/(a^2 +b^2)

熱心網友

asinx+bcosx+c=0---sin(x+f)=-c/√(a^2+b^2)[f=arctan(b/a)]---x1+f=-arc[c/√(a^2+b^2)];x2+f=Pi+arcsin[c/√(a^2+b^2)]---(A+f)+(B+f)=π---A+B=Pi-2f---sin(A+B)=-sin2f=-2tanf/[1+(tanf)^2]=-2(b/a)/[1+(b/a)^2]=-2ab/(a^2+b^2)

熱心網友

題目是不是有問題啊