# 20 分** 1 條Form 2 數,, 入黎睇下啦...

1 條Form 2 數...

http://img12.picsplace.to/img.php?file=img12/2/Mat...

答案係...

51.5

唔該講下點解...

最好有埋解釋...

最好果個會係最佳回答...

thx~

PS*

e 個係用畢氏定理計嫁...

### 3 Answers

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- 1 decade agoFavorite Answer
take the midpoint between AB as C,

the point where the pendulum is fixed as O,

the lowest point of the pendulum as D,

OD = 20cm

OC = OD - 5cm

= 15cm

consider triangle OAC,

OC^2 + AC^2 = OA^2

15^2 + AC^2 = 20^2

225 + AC^2 = 400

AC^2 = 175

AC = 13.2 cm (correct to 3 sig. fig.)

AB = 2AC

= 13.2 x 2

= 26.4 cm (correct to 3 sig. fig.)

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- 琴生Lv 51 decade ago
http://i179.photobucket.com/albums/w296/14022007/p...

請參考上圖.

OC = 20 cm - 5 cm = 15 cm

OA = 20 cm

By Pyth.Thm.,

CA2 = OA2 - OC2 = 202 - 152 = 175

CA = √175

AB = 2CA = 2√175 = 10√7

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- samLv 51 decade ago
do you mean horizonic distance between A and B

if so, your answer is wrong

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