標題:

微積分算誤差!!英文題目(簡單英文)

發問:

The side of a square is measured to be 10ft, with a possible error of +,- 0.1ft.A.Use differentials to estimate the error in the calculated area.B. Estimate the percentage errors in side and the area.The hypotenuse of a right triangle is known to be 10 in. exactly, and one of the acute angles is measured to be... 顯示更多 The side of a square is measured to be 10ft, with a possible error of +,- 0.1ft. A.Use differentials to estimate the error in the calculated area. B. Estimate the percentage errors in side and the area. The hypotenuse of a right triangle is known to be 10 in. exactly, and one of the acute angles is measured to be 30度, with a possible error of 正負0.5度 A.Use differentials to estimate the errors in the sides opposite and adjacent to the measured angle. B.Estimate the percentage errors in the sides.

 

此文章來自奇摩知識+如有不便請留言告知

最佳解答:

若是利用一次微分近似f(x+△x)= f(x) + f '(x)△x求解 (一)解 (A) 測量正方形面積,邊長 x=>令 f(x)=x2=>f '(x)= 2x,△x取 ±0.1 則f(10.1) = f(10)+ f '(10) × 0.1= 100+2=102 ( ft2 ) f(9.9) = f(10)- f '(10) × 0.1 = 98 ( ft2 ) 面積誤差為± 2 ( ft2 ) (B) 百分比誤差=實驗值與理論值間差距的絕對值,再除以理論值 則實驗邊長的百分比誤差為:|± 0.1|/10 = 1% 實驗面積的百分比誤差為:|± 2|/100 = 2% (二)解 當斜邊與鄰邊角度為 θ,則鄰邊長為 10cosθ,對邊長為 10sinθ 測量的 △θ 取 ± 0.5 cos(30.5° )= cos30°+ (cos30° )' × 0.5 = cos30°-sin30° × 0.5 = (2√3-1)/4 ≒ 0.616 cos(29.5° )= cos30°+(cos30° )' × (-0.5)=cos30°+sin30° × 0.5= (2√3+1)/4 ≒ 1.116 sin(30.5° )= sin30°+(sin30° )' × 0.5= sin30°+cos30° × 0.5= (2+√3)/4 ≒ 0.933 sin(29.5° )= sin30°+(sin30° )' × (-0.5)= sin30°-cos30° × 0.5=(2-√3)/4 ≒ 0.067 ∴鄰邊測量值為 10cos(30.5° )及 10cos(29.5° )各為 6.16 (inch) 和 11.16 (inch) 理論值為 10cos30° ≒ 8.66 ,誤差為 |±2.5|/8.66 ≒ 28.87% 對邊測量值為 10sin(30.5° )及 10sin(29.5° )各為 9.33 (inch) 和 0.67 (inch) 理論值為 10sin30° = 5,誤差為 |±4.33|/5 = 86.6% <另解> 利用一次微分近似的誤差還蠻大的,若是用高次近似來逼近的話,這題會算到死,不過若是利用馬克勞林級數求解近似值的話,會比較好算,誤差會很小很多,我在這舉一例即可,因為若全部打完也是很麻煩的 ∵馬克勞林級數sin x= x-(x3/3!)+(x^5/5!)-(x^7/7!)+ . . . . . . 計算一下誤差是 0.5 × π/180 ≒ 0.0087則計算到誤差小於 1/1000 即可 =>sin30°= sinπ/6=sin (0.523) = 0.523-(0.5233/3!)+(0.523^5/5!) ∵|sin0.523-(0.523-(0.5233/3!)|< (0.523^5/5!) ≒ 3.26 × 10^(-4)<10^(-3) ∴sin0.523≒ 0.523-0.5233/3! ≒ 0.499(相當接近理論值 sin30°= 0.5 ) 這樣可計算出實驗值的<對邊長>為 10sin0.523=4.99 (inch) 百分比誤差為 0.01/5 = 0.2% 同理,可利用馬克勞林級數 cos x = 1-(x2/2!)+(x^4/4!)-(x^6/6!)+ . . . . . . 來求出鄰邊的實驗值及其誤差

其他解答:5FAD1C75A5AA61DA
arrow
arrow

    wszspj2 發表在 痞客邦 留言(0) 人氣()