cos(75°+α)=1/3是吧?
∵ cos(75°+α)=1/3,其中α为第三象限角
∴75°+α为第四象限的角
∴sin(75°+α)=-√(1-(1/3)^2)=-2√2/3
sin(105°-α)+cos(α-105°)
=cos(105°-α)+sin(105°-α)
=cos[180°-(75°+α)]+sin[180°-(75°+α)]
=-cos(75°+α)+sin(75°+α)
=- 1/3- (2√2/3)
= -(2√2+1)/3
故答案为:-(2√2+1)/3
已知(75°+α)=1/3,α为第三象限角,求sin(105°-α)+cos(α-105°)的值
已知(75°+α)=1/3,α为第三象限角,求sin(105°-α)+cos(α-105°)的值
数学人气:923 ℃时间:2020-01-30 11:57:43
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