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# Trig graph question help watch

I hope the question is clear in the pic.
2. a) a is the y-intercept so a = 1.
b is the amplitude of the sine wave (height from average) so b= 3 - 1 = 2.
Notice that the sine wave is 18 units long, so its maximum is at at t = 9/2. The maximum occurs when sin(pi t/c) = 1, which is when pi t/c = pi/2, hence c = 2 * 9/2 = 9.

b) 3 points by inspection (draw the line).

c) t = 9 is half way along the sine curve so the y-value is 1. The line l has equation (y - 3)/(x - 0) = (-1 - 3)/(18 - 0), since x = 9, we have y = 3 - 9 * 2/9 = 1. The y-values are the same so the point on the curve is also on l.

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Updated: October 10, 2013
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