求值(tan5°-cos5°)sin20°/1+cos20°

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求值(tan5°-cos5°)sin20°/1+cos20°

求值(tan5°-cos5°)sin20°/1+cos20°
求值(tan5°-cos5°)sin20°/1+cos20°

求值(tan5°-cos5°)sin20°/1+cos20°
(tan5°-cot5°)sin20°/(1+cos20°)
=(sin5º/cos5º-cos5º/sin5º)/(2cos²10º)
=[(sin²5º-cos²5º)/(sin5ºcos5º)]/(2cos²10º)
=-2[(cos10º/(sin10º)]/(2cos²10º)
=-[1/(sin10º)]/(cos10º)
=-2/(2sin10ºcos10º)
=-2/sin20º