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Sin Graphs

For confirmation purposes.

If given coordinates on a sin graph (2,5) and I am asked to label a and b. Y= A sin (bx)

I know that my a would be 5.

The x and y co coordinates are central between 0-180degrees at the peak of the parabola.

Based on the transformation rules, I know that
F(qx) is 1/q, therefore I am assuming b= 90/2 which would give me 45.
Reply 1
Avatar for mqb2766
mqb2766
21
Original post by KingRich
For confirmation purposes.

If given coordinates on a sin graph (2,5) and I am asked to label a and b. Y= A sin (bx)

I know that my a would be 5.

The x and y co coordinates are central between 0-180degrees at the peak of the parabola.

Based on the transformation rules, I know that
F(qx) is 1/q, therefore I am assuming b= 90/2 which would give me 45.

Can you upload the original question / graph?
Reply 2
Avatar for KingRich
KingRich
OP
14
Original post by mqb2766
Can you upload the original question / graph?

B9681D29-ED05-46F3-AE7A-792331AE8D6A.jpeg
Reply 3
Avatar for mqb2766
mqb2766
21
Original post by KingRich
B9681D29-ED05-46F3-AE7A-792331AE8D6A.jpeg

So the point is a maximum, so a must be 5 as you say and b would be 45 degrees as 2*45 = 90 which corresponds to the sin peak.
Reply 4
Avatar for KingRich
KingRich
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14
Original post by mqb2766
So the point is a maximum, so a must be 5 as you say and b would be 45 degrees as 2*45 = 90 which corresponds to the sin peak.

So, it’s as I presumed? Half of 180 is 90 degrees, therefore 90x1/2 is 45. Likewise if x was 3 then it would be 90x1/3= 30 ?
Reply 5
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mqb2766
21
Original post by KingRich
So, it’s as I presumed? Half of 180 is 90 degrees, therefore 90x1/2 is 45. Likewise if x was 3 then it would be 90x1/3= 30 ?

Largely yes. No need for the bold part as you should know the sin() peak occurs at 90, but the rest is good. If you're unsure, "guess" and check so
5sin(30*3) = 5sin(90) = 5
(edited 2 years ago)
Reply 6
Avatar for KingRich
KingRich
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14
Original post by mqb2766
Largely yes. No need for the bold part as you should know the sin() peak occurs at 90, but the rest is good. If you're unsure, "guess" and check so
5sin(30*3) = 5sin(90) = 5

I don’t know where the bold text came from. That’s a little strange, but thank you for confirmation
Reply 7
Avatar for mqb2766
mqb2766
21
Original post by KingRich
I don’t know where the bold text came from. That’s a little strange, but thank you for confirmation

I added the bold emphasis just to say all you need to say is that the peak occurs at 90. You don't need to relate it to 0 - 180.
Reply 8
Avatar for KingRich
KingRich
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14
Original post by mqb2766
I added the bold emphasis just to say all you need to say is that the peak occurs at 90. You don't need to relate it to 0 - 180.

Oh, okay. Thank you

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