(sin10°+sin20°)/(cos10°+cos20°)化简求值

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(sin10°+sin20°)/(cos10°+cos20°)化简求值
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(sin10°+sin20°)/(cos10°+cos20°)化简求值
(sin10°+sin20°)/(cos10°+cos20°)化简求值

(sin10°+sin20°)/(cos10°+cos20°)化简求值
(sin10°+sin20°)/(cos10°+cos20°) (和差化积得到下式)
=2sin15°cos5°/(2cos15°cos5°)
=tan15°
=tan(45°-30°)
=(1- tan30°)/(1+ tan30°)
=(1- 根号3/3)/(1+ 根号3/3)
=(3-根号3)/(3+根号3)
=(3-根号3)²/[(3+根号3)(3-根号3)]
=(12-6根号3)/6
=2 - 根号3