How Do You Model Desert Temperature Variations Mathematically?

Quantum_Grid
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Homework Statement


The desert temperature, H, oscillates daily between 40 degrees F at 5 am, and 80 degrees F at 5 pm. Write a possible formula for H in terms of t, measured in hours from 5 am.


The Attempt at a Solution


The best I can come up with is

H=60+40sin((pi/6)t)

but this does not look right when I try and graph it on a calculator. I think the 40sin part is what I have wrong, but I cannot figure out what goes there, and the book is no help at all. Am I at least close?
 
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The amplitude of the oscillation is 40, but multiplying the base function by 40 will make it oscillate between -40 and 40, giving it an amplitude of 80. Ie., your function oscillates between 60 - 40 = 20 and 60 + 40 = 100.
 
OK, I looked a little closer and I think they want it to start at 40. So I got H=60+(-20)cos((pi/12)t)

I think I had the period wrong too... This looks right...right?
 
Quantum_Grid said:
OK, I looked a little closer and I think they want it to start at 40. So I got H=60+(-20)cos((pi/12)t)

I think I had the period wrong too... This looks right...right?

Looks great!
 
There are two things I don't understand about this problem. First, when finding the nth root of a number, there should in theory be n solutions. However, the formula produces n+1 roots. Here is how. The first root is simply ##\left(r\right)^{\left(\frac{1}{n}\right)}##. Then you multiply this first root by n additional expressions given by the formula, as you go through k=0,1,...n-1. So you end up with n+1 roots, which cannot be correct. Let me illustrate what I mean. For this...
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