Posted by **trig** on Thursday, May 7, 2009 at 5:46pm.

study of sunspots. spots in a year min. is 10, max is 110. between max's of 1750 & 1948, 18 cycles occurred. Find a sinusoidal equation to model this.

My equation looks something like this so far:

y=50sin(2pi/11(x-d))+60

so How do I get the phase shift? d? I am confused about what would be x and y to plug into the formula and find d? Because the max occurs at 1750, but what would be the x and y values to sub in and why?

- Anonymous -
**Damon**, Thursday, May 7, 2009 at 5:58pm
y=50sin( 2pi(x-d)/11 )+60

when x = 1750, you have a max and sin (2 pi(1750-d)/11) = 1

or 2 pi (1750-d)/11 = pi/2 (90 degrees for max of sin function)

1750-d =11/4 (in other words a quarter of a cycle after start)

d = 1750 - 11/4

- Anonymous -
**trig**, Thursday, May 7, 2009 at 6:02pm
How did you get 1750-d=11/4?

- Anonymous -
**trig**, Thursday, May 7, 2009 at 6:10pm
I mean, so would d = 1747.25

ie

y=50sin(2pi/11(x-1747.25))+60

## Answer This Question

## Related Questions

- Calculus - Find any absolute max/min and local max/min for the function f(x)=x^3...
- trig - I have finished the questions for the following, but could someone please...
- PreCalc - y =( (C-A)/2 ) sin( (X - (A - ( (C - A)/2 ) ) )( pi/(C-A) ) ) + (B...
- MAth - If 1 gallon (gal) of water weighs 8.34 pounds (lb), how much does 3.75 ...
- Math - For each of the following quadratics, determine if the equation has a max...
- Algebra 2 - Please help super confused!!! Which points are the best ...
- Math - Find the critical points and the interval on which the given function is ...
- Physics- uncertainty - Eileen, Jackie, and Kathryn needed to find the difference...
- math - how to solve this problem: max min(x-y)..... here where the max have ...
- Calculus - Find any absolute maximum and minimum and local maximum and minimum ...

More Related Questions