求(sin40°+cos10°)/cos20° =(cos50°+cos10°)/cos20°

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求(sin40°+cos10°)/cos20° =(cos50°+cos10°)/cos20°
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求(sin40°+cos10°)/cos20° =(cos50°+cos10°)/cos20°
求(sin40°+cos10°)/cos20° =(cos50°+cos10°)/cos20°

求(sin40°+cos10°)/cos20° =(cos50°+cos10°)/cos20°
(sin40°+cos10°)/cos20°
=【cos(π/2-40°)+cos10°】/cos20°
=(cos50°+cos10°)/cos20°

cos50°=cos(pi/2-40°)=sin40°
所以(sin40°+cos10°)/cos20° =(cos50°+cos10°)/cos20°

sin40=cos(90-40)=cos50

sin(90°-50°)=cos50°就这样好了、、、