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# In need of some trig help! Watch

1. Hey so I'm a bit stuck on this core question:

For each state
i) The amplitude
ii) The period
iii) the maximum value
iv) the smallest possible value of x at which the function is at maximum value

for these functions...

a) y = 3sin(2x - 153)+4
b) y = 1.75 cos (123-3x)-3

I've tried the first function, and I think the amplitude is 3, the period is 180 and the max value is 7, but those are just guesses which I'm sure are wrong...

2. I agree with your 'guesses'

How did you work them out?
3. hehe well because it's 3 multiply the sin(x.....) so i guess the amplitude must be that. And yeah I just used methods that I was taught to find the others lol

But yeah I'm not really sure about the fourth question of the smallest possible value of x, so do you have any idea on that?

And also does the '-153' in the function affect any of the questions?
4. Yup. Since sin(stuff) always goes between -1 and 1, 3 times that will vary between -3 and 3, meaning that the amplitude is 3 and 4+3sin(stuff) can and will hit 7, but no higher.

Find the function's minimum value in the same way as you found it's maximum value, then work out what 'stuff' has to be for sin(stuff) to be at a minimum. There will be loads of possible values (sine is periodic, after all), and you need to work out what is the smallest value of x that gives one of those.
5. o ok, so i got 31.5 for the that part, is it right?
6. Yeah, I'd agree with that

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Updated: December 9, 2010
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