Question

Ru.(ฅ´ω`ฅ)

請問這兩題怎麼寫><

?設COS170°=k,則以K表 sin280°=
8. 若 cos67°cos90% cosb三数成等差数列,且90<<180° 則
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=

Answer 1

✨ 最佳解答 ✨

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7.
注意到170°+280°=450°=360°+90°
280°=360°+90°-170°
sin(280°)=sin(90°-170°)=cos(170°)=k
8.
cos67°+cosθ=2cos90°=0
cosθ= - cos67°=cos(180°-67°)
θ=113°