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问题: 请帮忙化简

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

解答:

(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