求feather的值令d離ob最遠，且求該最遠距離,準確至三位有效數字
題目如下(圖片網址):
https://imagizer.imageshack.us/v2/565x418q90/r/540/V61v5M.png
求h
題目如下(圖片網址):
https://imagizer.imageshack.us/v2/565x418q90/r/537/vwP4Yg.png
求解以下中二數學題,10點!
2014-08-24 2:09 am
回答 (4)
2014-08-24 1:57 pm
✔ 最佳答案
(1) D is farthest from OB when BD is perpendicular to OB, that is angle OBD = 90 degree. That means angle OBA + angle ABD = 90 degreeangle OBA = theta
angle ABD = arctan (45/120)
so theta = 90 - arctan (45/120)
(2)
By Pythagoras thm., BC = sqrt (12^2 + 16^2) = 20
Area of triangle = (20h)/2 = (12 x 16)/2
so h = 12 x 16/20 = 9.6
2014-08-24 4:26 am
建議使用 Pyth theorem
2014-08-24 3:27 am
求h :
tan ∠ACB = 12/16
∠ACB = 36.87⁰
∠ACD = 90⁰ - ∠ACB = 53.13⁰
h = 16 cos53.13⁰ = 9.6 m
2014-08-23 19:30:00 補充：
上1題，
距離 = 120 sinθ + 45sin(90⁰ - θ)
= 120 sinθ + 45cosθ
求最大?? 中二?? 唔識做！
tan ∠ACB = 12/16
∠ACB = 36.87⁰
∠ACD = 90⁰ - ∠ACB = 53.13⁰
h = 16 cos53.13⁰ = 9.6 m
2014-08-23 19:30:00 補充：
上1題，
距離 = 120 sinθ + 45sin(90⁰ - θ)
= 120 sinθ + 45cosθ
求最大?? 中二?? 唔識做！
收錄日期: 2021-04-27 20:35:06
原文連結 [永久失效]:
https://hk.answers.yahoo.com/question/index?qid=20140823000051KK00103