若f(X)=sin(π+x)cos(2π-x)/cos(π/2+x),求f(π/3)的值
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若f(X)=sin(π+x)cos(2π-x)/cos(π/2+x),求f(π/3)的值
若f(X)=sin(π+x)cos(2π-x)/cos(π/2+x),求f(π/3)的值
若f(X)=sin(π+x)cos(2π-x)/cos(π/2+x),求f(π/3)的值
化简得:
f(X)=cosX 带入π/3得1/2
f(X)=sin(π+x)cos(2π-x)/cos(π/2+x)
=-sinxcosx/-sinx
=cosx
当x=π/3时
f(x)=1/2
sin(π+x)cos(2π-x)/cos(π/2+x)=-sinx cosx/(-sinx)=cosx=f(x)
f(π/3)=cos(π/3)=0.5
你好:
f(兀/3)=sin(兀 兀/3)cos(2兀-兀/3)/cos(兀/2 兀/3)推出
f(兀/3)=-sin(兀/3)cos(兀/3)/-sin(兀/3)推出
f(兀/3)=cos(兀/3)=1/2
说白了这是考公式的,最重要的是理解