# Find C in general sine function

Endorser
Hello All,

I am just wondering how to find c in the sine function (y=asinb(x-c)+d).

I understand wat the values mean and how to find a b and d but c i am not to sure how to find unless there is a already given graph.

thanks

## Answers and Replies

Homework Helper
c is the horizontal displacement of the graph: it shifts the graph of a sin(bx) + d to the right by c units.

I understand [...] how to find a b and d but c i am not to sure how to find unless there is a already given graph.
I don't quite get that. You cannot get a, b and d without a given graph either, or you need some other information to find them but then you can usually also find c...

Endorser
I don't quite get that. You cannot get a, b and d without a given graph either, or you need some other information to find them but then you can usually also find c...

I will give you an example of what i mean, check attachments below

#### Attachments

• Example.png
27.6 KB · Views: 2,640
Homework Helper
The value of c is hidden in the sentence "high tide is at midnight".
If the c weren't there (or would be 0) then the maximum of the sine would be at $b x = \pi / 4$.
Replacing x by (x - c) shifts it horizontally, such that you can put the maximum at t = 0 (if that would be midnight).

Endorser
If the c weren't there (or would be 0) then the maximum of the sine would be at $b x = \pi / 4$.
Replacing x by (x - c) shifts it horizontally, such that you can put the maximum at t = 0 (if that would be midnight).

ahh so in this case i must place the highest tide at midnight and then find point d to find c
I am still confused because if u graph y=asinbx+d which is water your saying to do then find c but the graph of y=asinb(x-c)+d (provided that a b and d are constant) the graph is different