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Cos25

cos(25°) = 0.90630778703665

cos25度大约等于 0.906

tan25°是≈0.47 sin25°≈0.42 cos25°≈0.91 望采纳,谢谢!

等于75度的正弦值,然后75写成30+45用公式就行了。

(√3)/2

(cos85°+sin25°cos30°)/cos25° = {cos(60°+ 25°) + sin25°cos30°} /cos25° = {cos60°cos25° - sin60°sin25° + sin25°cos30°} /cos25° = {cos60°cos25° - sin25°(sin60° - cos30°) } /cos25° = cos60°cos25° / cos25° = cos60° = 1/2

=cos25cos20-cos(90-20)cos(90-25) =cos25cos20-sin20sin25 =cos45=√2/2

√2/2 √(2+√2)/2 √(√(2+√2)+2)/2 √是根号下 ≈ 0.707 0.924 0.981

cos40°/(cos25°√1-sin40°) =cos40°/[cos25°√(cos20°-sin20°)^2] =cos40°/[cos25°(cos20°-sin20°)] =(cos20°-sin20°)(cos20°+sin20°)/[cos25°(cos20°-sin20°)] =(cos20°+sin20°)/cos25° =√2 (cos20°sin45+sin20°cos45)/cos25° =√2sin65°/cos25° =...

cos(25°)=0.90630778703665

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