求值:cos(x+27°)cos(x-18°)+sin(x+27°)sin(x-18°) 急救急救!
1个回答
cos(x+27°)cos(x-18°)+sin(x+27°)sin(x-18°)
=cos[(x+27°)-(x-18°)].cos两角差公式
=cos45°
=√2/2
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