化简
化简:cos`4 a/2-sin`4 a/2 化简:sin50°〔1+√3tan10°〕
化简:cos^4 (a/2)-sin^4( a/2 ) =[cos²(a/2)+sin²(a/2)][cos²(a/2)-sin²(a/2)] =1×cosa =cosa。 化简:sin50°〔1+√3tan10°〕 =sin50°[1+√3·(sin10°/cos10°)] =sin50°[(cos10°+√3·sin10°)/cos10°] =sin50°[2(1/2·cos10°+√3/2·sin10°)/cos10°] =sin50°[2sin°(30°+10°)/cos10°] =(2sin50·sin40)/cos10° =(2cos40°·sin40°)/cos10° =sin80°/cos10° =cos10°/cos10° =1。
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