9514 1404 393
Answer:
a) 102.4
b) 72.6
c) 87.5
Step-by-step explanation:
The average value of a function over an interval is the integral of that function over the interval, divided by the width of the interval.
(a) The summer average is ...
[tex]\text{summer average}=\displaystyle\dfrac{1}{(\frac{1}{4})}\int_\frac{1}{2}^\frac{3}{4}{T(x)}}\,dx=87.5+23.4\cdot\dfrac{2}{\pi}\approx 102.4[/tex]
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(b) The winter average is similar:
[tex]\text{winter average}=87.5-23.4\cdot\dfrac{2}{\pi}\approx 72.6[/tex]
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(c) The annual average is the value added to the cosine function: 87.5
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Additional comment
The integral of the cosine function over the period of interest is ...
∫cos(2πx)dx = 1/(2π)sin(2πx)
For the limits x=1/2 and x=3/4, this becomes 1/(2π)(-1 -0) = -1/(2π).
When multiplied by -23.4(1/(1/4)), we get +23.4(2/π).
