(1/cos^80°-3/cos^10°)×1/cos20°=(详细过程)
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![(1/cos^80°-3/cos^10°)×1/cos20°=(详细过程)](/uploads/image/z/389902-22-2.jpg?t=%EF%BC%881%2Fcos%5E80%C2%B0-3%2Fcos%5E10%C2%B0%EF%BC%89%C3%971%2Fcos20%C2%B0%3D%EF%BC%88%E8%AF%A6%E7%BB%86%E8%BF%87%E7%A8%8B%EF%BC%89)
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(1/cos^80°-3/cos^10°)×1/cos20°=(详细过程)
(1/cos^80°-3/cos^10°)×1/cos20°=(详细过程)
(1/cos^80°-3/cos^10°)×1/cos20°=(详细过程)
(1/cos^280-3/cos^210)*(1/cos20)
=(1/cos^2(90-10)-3/cos^210)(1/cos20)
=(1/sin^210-3/cos^210)*(1/cos20)
=(cos^210-3sin^210)/(sin^210*cos^210)*(1/cos20)
=(4cos^210-3)/(sin^210*cos^210)*(1/cos20)
=(2cos20-1)/(sin^210*cos^210)*(1/cos20)
=4(2cos20-1)/(sin^210*cos^210)*(1/cos20)
=8 (cos20 - cos60 ) / sin^220 *(1/cos20)
=16sin40sin20 / sin^220 *(1/cos20)
=32 cos20 *(1/cos20)
=32
=32