1. Given that cos ( 2x-15) = sin35 , find the value of x without the use of calculator.
2 Mary measured the weight of 50 $1 coins and the measurement is 350g, correct to the nearest g.
(a) Find the percentage error of this measurement.
(b) If Mary uses the weight of 50 $1 coins to estimate the weight of each $1 coin, find the maximum absolute error of the weight of each $1 coin
percentage error and cos thing
2009-08-14 5:53 am
回答 (2)
2009-08-14 6:36 am
✔ 最佳答案
1)cos ( 2x-15) = sin35 cos(2x-15)=cos(90-35)
2x-15=55
2x=70
x=35
2a)(1X0.5/350)X100%
=(0.5/350)X100%
=14.3%,cor.to 3sig.fig
2b)
the maximum absolute error of the weight of each $1 coin
=1X0.5/50
=0.01
參考: me
2009-08-14 6:37 am
1. cos(2x – 15) = sin35, assuming all angles are with 0 to 90
cos(2x – 15) = cos(90 – 35)
2x – 15 = 90 – 35
2x = 55 + 15
x = 35
2 (a)
The absolute maximum error of the measurement is 0.5g
The percentage error = 0.5/350 x 100% = 0.143%
(b)
The estimated weight of a coin = 350g / 50 = 7g
The maximum absolute error of the weight = 7g * 0.143% = 0.01g
Alternatively, since the absolute maximum error for the 50 coins is 0.5g, the absolute maximum error for one coin is 0.5g/50 = 0.01g.
cos(2x – 15) = cos(90 – 35)
2x – 15 = 90 – 35
2x = 55 + 15
x = 35
2 (a)
The absolute maximum error of the measurement is 0.5g
The percentage error = 0.5/350 x 100% = 0.143%
(b)
The estimated weight of a coin = 350g / 50 = 7g
The maximum absolute error of the weight = 7g * 0.143% = 0.01g
Alternatively, since the absolute maximum error for the 50 coins is 0.5g, the absolute maximum error for one coin is 0.5g/50 = 0.01g.
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