ctg平方a乘以seca-1/sina+1 再加上sec平方a 乘以sina-1/seca+1

熱心網友

(ctga)^2 (seca-1)/(sina+1) +(seca)^2 (sina-1)/(seca+1)=[(ctga)^2 (seca-1)(seca+1)+(seca)^2 (sina-1)(sina+1)]/(sina+1)(seca+1)={(ctga)^2 [(seca)^2 -1)]-(seca)^2 [1-(sina)^2]}/(sina+1)(seca+1)=[(ctga)^2 (tga)^2 -(seca)^2 (cosa)^2]/(sina+1)(seca+1)=(1-1)/(sina+1)(seca+1)=0