#1**+10 **

A sign wave is of the form (I am developing the graph in radians)

y=sinx

This has a amplitude of 1 a centre y=0 and a wavelength of 2pi

\(y=sin(x) \qquad \text{ has a wavelength of }2\pi\\\ y=sin(nx) \qquad \text{ has a wave length of } 2\pi\div n\ so\\ y=sin(\frac{2\pi }{24} *x) \qquad \text{ has a wave length of }2\pi\div \frac{2\pi }{24}=24 \text{ and this will represent hours.}\\\)

So so far we have

\(y=sin[\frac{2\pi}{24}(x)]\)

Now the amplitude of the wave is 15 degrees (80-65=15)

\(y=15sin[\frac{2\pi}{24}(x)]\)

The centre of the wave is y=65 so the wave is 'lifted' by 64

\(y=15sin[\frac{2\pi}{24}(x)]+65\)

The hottest part of the day is 5pm=17:00 in 24 hour time, so the average temps must be 6 hours either side, 11:00 and 23:00

So at 11:00 the is average temp but getting hotter. So the horizonal shift is 11 in a positive direction

\(y=15sin[\frac{2\pi}{24}(x-11)]+65\)

So at 3am it will be

15*sin(2pi/24(3-11))+65 = 52 degrees

Here is the graph:

Full interactive version:

https://www.desmos.com/calculator/uri6zjnpns

picture version:

Melody
Feb 18, 2017

#1**+10 **

Best Answer

A sign wave is of the form (I am developing the graph in radians)

y=sinx

This has a amplitude of 1 a centre y=0 and a wavelength of 2pi

\(y=sin(x) \qquad \text{ has a wavelength of }2\pi\\\ y=sin(nx) \qquad \text{ has a wave length of } 2\pi\div n\ so\\ y=sin(\frac{2\pi }{24} *x) \qquad \text{ has a wave length of }2\pi\div \frac{2\pi }{24}=24 \text{ and this will represent hours.}\\\)

So so far we have

\(y=sin[\frac{2\pi}{24}(x)]\)

Now the amplitude of the wave is 15 degrees (80-65=15)

\(y=15sin[\frac{2\pi}{24}(x)]\)

The centre of the wave is y=65 so the wave is 'lifted' by 64

\(y=15sin[\frac{2\pi}{24}(x)]+65\)

The hottest part of the day is 5pm=17:00 in 24 hour time, so the average temps must be 6 hours either side, 11:00 and 23:00

So at 11:00 the is average temp but getting hotter. So the horizonal shift is 11 in a positive direction

\(y=15sin[\frac{2\pi}{24}(x-11)]+65\)

So at 3am it will be

15*sin(2pi/24(3-11))+65 = 52 degrees

Here is the graph:

Full interactive version:

https://www.desmos.com/calculator/uri6zjnpns

picture version:

Melody
Feb 18, 2017

#3

#4**0 **

Thanks Chris,

I am sure it can be done much easier, the time is not a difficult one, but I just decided to do it like this.

I suppose if I was good at it, and did not have to think at all, it would be a dead simple method but at present I still have to think about what is happening.

Melody
Feb 18, 2017