Terony
春芽
共回答了13个问题采纳率:100% 举报
(1+sin70°)/(2*sin20°)-sin10°(cot5°-tan5°)
=(1+cos20°)/(2sin20°)-sin10°(cot5°-tan5°)
=2(cos10°)^2/(2sin20°)-sin10°(cos5°/sin5°-sin5°/cos5°)
=cos10°/(2sin10°)-sin10°cos10°/(sin5°cos5°)
=(cos10°-4sin10°cos10°)/(2sin10°)
=(cos10°-2sin20°)/(2sin10° )
=(cos10°-2sin(30°-10°)/(2sin10° )
=cos30°sin10°/(2sin10°)
=cos30°
=√3/2
1年前
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