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# Trig curves translation help watch

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1. Hi, I have to draw the graph of d= 5-4sin(30t)' (the ' is the degrees sign)
The question is about depth of water (d) compared to time after midnight (t)and you have to plot the graph of it. I understand the 5 would make the graph translate upwards by 5 and the -4sin make the graph enlarge (stretch upwards) by 4 then flip, but what does the 30t mean??? thank you!!
2. (Original post by mayjb)
Hi, I have to draw the graph of d= 5-4sin(30t)' (the ' is the degrees sign)
The question is about depth of water (d) compared to time after midnight (t)and you have to plot the graph of it. I understand the 5 would make the graph translate upwards by 5 and the -4sin make the graph enlarge (stretch upwards) by 4 then flip, but what does the 30t mean??? thank you!!
This may be better off in the Maths forum.

If you just start off with sin(30t), you can apply what you've correctly identified about the -4 and the 5. Sin(30t) is the tricky bit.

Think of the x axis as t, and think about the period of sin. For sin(x) as x goes from 0 to 360, it does one complete 'cycle'.

For what values of t does sin(30t) do a complete cycle? (Or if it's easier, for what values of 30t does sin(30t) do a complete cycle, if we call 30t = x)?

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Updated: February 21, 2016
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