# Sin Graphs

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Thread starter 1 month ago
#1
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.
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1 month ago
#2
(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?
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Thread starter 1 month ago
#3
(Original post by mqb2766)
Can you upload the original question / graph?
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1 month ago
#4
(Original post by KingRich)
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.
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Thread starter 1 month ago
#5
(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 ?
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1 month ago
#6
(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
Last edited by mqb2766; 1 month ago
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Thread starter 1 month ago
#7
(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
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1 month ago
#8
(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.
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Thread starter 1 month ago
#9
(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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