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# Trigonometry AS P1 watch

1. May someone please explain this question to me?
It seems straightforward but I don't understand it sorry.

https://gyazo.com/c3ed58404f292f17280c4e115b20b3ff
2. Hi, you can think of this like y = bsinx a

It's a graph of 2sinx that's been moved up by 1, so a=1 and b=2 (If you move it all down by 1 you'll see that it is a normal sin graph, but goes between -2 and 2, so has been stretched upwards by times 2)

I don't know what the answer is, or if that's right, but that's what I'd put.

Sorry if that explanation was horrible lol, but hope that helps
3. Uhmm the answer is correct , but I dont understand it Its probably because I need to learn the trigonometric graphs, I can do all the trigonometic equations and identities questions without knowing the trig graphs tho...

What does the a and b supposed to be in the graph?

Thanks!
4. (Original post by Jian17)
Uhmm the answer is correct , but I dont understand it Its probably because I need to learn the trigonometric graphs, I can do all the trigonometic equations and identities questions without knowing the trig graphs tho...

What does the a and b supposed to be in the graph?

Thanks!
You are right - you do need to learn the shapes of the trig graphs. But this is really about linear transformation of a function. y = a + bsinx is a linear transformation of y = sinx with a vertical stretch factor of b and a vertical shift of a.
5. Oh okay, no worries!

The +a is going to translate the graph vertically (so +1 will move the whole thing up by 1)

bsinx means that you'll have a sinx graph that has been stretched by b (so 2sinx means times all the y coordinates by 2)

Use BIDMAS, so you have to times the Y coordinates by 2 first and then shift the whole graph up by 1.

Sorry if this isn't making too much sense, someone much better at explaining than me should see this soon!
6. (Original post by Jian17)
May someone please explain this question to me?
It seems straightforward but I don't understand it sorry.

https://gyazo.com/c3ed58404f292f17280c4e115b20b3ff
I got 1+2sinx

The way I did it was by looking at the graph . I used the coordinate (0,1) to find a , then use coordinate (1/2pi,3) to find the value of b .
7. (Original post by HelloImCool)
I got 1+2sinx

The way I did it was by looking at the graph . I used the coordinate (0,1) to find a , then use coordinate (1/2pi,3) to find the value of b .
I don’t know if this is the best way to approach it though. I just used simple algebra

I self quoted myself sorry
8. Thanks everyone for their help! I understand it better now, I will ask my teacher to explain it to me too when i can just to make sure i understand the concept tho
9. (Original post by HelloImCool)
I got 1+2sinx

The way I did it was by looking at the graph . I used the coordinate (0,1) to find a , then use coordinate (1/2pi,3) to find the value of b .
Why did you use the coordinate 1/2pi,3 to find b?? I can see why you used 0,1 but the other one :s
10. (Original post by Jian17)
Why did you use the coordinate 1/2pi,3 to find b?? I can see why you used 0,1 but the other one :s
You’re over complicating it.

y = sinx is a periodic function with a minimum value of -1 and a maximum value of +1. The difference between the two is 1 - (-1) = 2.

The transformation of y = sinx shown in the diagram is a periodic function with a minimum value of -1 and a maximum value of 3. The difference between the two is 3 - (-1) = 4. So the stretch factor b is .....
11. (Original post by Jian17)
Why did you use the coordinate 1/2pi,3 to find b?? I can see why you used 0,1 but the other one :s
3=1+b(sin(90)) —> sin 90 =1

3=1+b
2=b

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