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ΪʲôCos(-x)=Cosx

һλ԰ ǣһxһ-x Կcosx=OA/R //: ҺĶ cos(-x)=OA/R ˣ cos(-x) = cosx ͼ

Ƶ̽⣺ 1ǿǺĹʽ cos(x) = cos(0-x) = cos0cosx+sin0sinx = cosx 2ͬʱҲǺֱ۵ xһǣôĸ-x֮XԳƣޣcos(-x)...

Ϊy=cosxż cos(-x)cosx

1ݹʽcos(A+B)=cosA*cosB-sinA*sinB, A=B=Xɵùʽ 2ԭʼ֪ʶʼƵ ȽֱϵֱϵxOyλԲOa,b-bʹaĿΪOxԲOڵP1ձ߽ԲOڵP2bʼΪOP2ձ߽ԲO...

Ϊcos(360-x)=cosx ԣ cos(180+x)=cos[360-(180+x)]=cos(180-x) Ƕ-cosx

Ϻ󵼡

cosx * cos(x+) ݻͲʽ ԭʽ = 1/2{cos(x+x+)+cos(x+-x)} = (1/2)cos(2x+) + (1/2)cos

Ϊ180= ߦ-xڵڶ,Ϊ,cos(-x=-cosx עcosxڵһΪ,ڶΪ.

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arccos֪cos=x arccosx=֮cos=cos(arccosx)=x 😊😊😊😊😊😊😊😊😊😊😊

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