# This worksheet contains the Maple commands from Chapter 3 of 
# Introduction to Scientific Programming by Joseph L. Zachary.
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# 
# (3.4)  This calculates the circumference of the earth in kilometers, 
# beginning from Eratosthenes's measurements.
# 
> 360 / 7.2 * 5000. * 0.1575;
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# 
# (3.5)  We can save the value of the expression from (3.4) into the 
# variable "circumference" by using an assignment statement.
# 
> circumference := 360 / 7.2 * 5000. * 0.1575;
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# 
# (3.6)  Now that we have given "circumference" a floating-point value, 
# we can use it as if it were a floating-point number.  We can, for 
# example, determine its value.
# 
> circumference;
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# 
# (3.7)  We can also use its value in more complicated expressions.
# 
> diameter := circumference / 3.14159;
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# 
# (3.8)  Here we recompute "circumference" using parentheses to explicitly 
# group the operands and operators from (3.5).
# 
> circumference := (360 / 7.2) * (5000. * 0.1575);
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# 
# (3.9)  The "Digits" variable is consulted by Maple to determine how 
# many digits to use in the mantissas of floating-point numbers.  Its value 
# can be modified via assignment.
# 
> Digits := 4;
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# 
# (3.10)  Now when we repeat the calculation from (3.5), we obtain a 
# four-digit result.  (Maple adds the trailing zero so that the magnitude of 
# the result will be correct.)
# 
> four_digit_circum := 360 / 7.2 * 5000. * 0.1575;
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# 
# (3.11)  We can also obtain a four-digit approximation to the earth's 
# diameter.
# 
> four_digit_diameter := four_digit_circum / 3.1;
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# 
# Let's set the mantissa size back to ten.
# 
> Digits := 10;
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# 
# (3.12)  This is part of an interval arithmetic computation.  We use the 
# smallest possible value (7.15) for the angle measured by Eratosthenes, 
# the largest possible value (5050) for the distance from Alexandria to 
# Cyrene, and the largest possible value for the conversion factor from 
# stadia to kilometers.  This gives us the largest possible value for the 
# circumference of the earth.
# 
> (360 / 7.15) * 5050. * 0.15755;
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# 
# (3.13)  We compute the smallest possible value for the circumference of 
# the earth by perturbing the measurements in the other direction.
# 
> (360 / 7.25) * 4950. * 0.15745;
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>