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March 31, 2015

March 31, 2015

Posted by **DK** on Monday, May 4, 2009 at 7:21pm.

My work:

So far I have

y=10sin(pi/20,000(x-d))+70

How do I get d? Can someone clearly explain to me how to get the phase shift? thanks

- trig -
**Reiny**, Monday, May 4, 2009 at 8:00pmmake use of the fact that if

x = 2000 , y = 80

80 = 10sin(pi/20000(2000-d))+70

10 = 10sin(pi/20000(2000-d))

1 = sin(pi/20000(2000-d))

so (pi/20000(2000-d)) = pi/2

(2000-d)/10000 = 1

2000-d = 10000

d = -8000

so your equation is

y=10sin(pi/20000(x+8000))+70

(check: sub in x = 2000, it works

y = 80)

- trig -
**DK**, Monday, May 4, 2009 at 8:21pmWhen I sub in x=2000, I get y=82.88 on my calculator?

How do I solve it to get 80?

- trig -
**DK**, Monday, May 4, 2009 at 8:23pmNVM, I got it

Thank you for your help!

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