need help with sin / cos useage

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i understand how to solve a given equation and graph it using sin and cos when im told what to use. I was given this question and am at a loss how im supposed to know what function to use in order to graph it.

A point on cam is 8.30cm from the center of a rotation. The cam is rotating with a constant angular velocity, and the vertical displacement d = 8.30cm for t = 0s. sketch two cycles of d as a function of t for the given values. The rotation is counterclockwise if that matters.

f = 3.20Hz

the form of the equation is d=R(cos/sin)wt.

im am able to find w = 2pi(f)= 20.106 or so and the form of the function is d=8.3____20.106. i just dont get how i know what function to use.

any help would be greatly appreciated as im being tested on this on Monday. Thanks

 

[Deleted member 4993]

i understand how to solve a given equation and graph it using sin and cos when im told what to use. I was given this question and am at a loss how im supposed to know what function to use in order to graph it.

A point on cam is 8.30cm from the center of a rotation. The cam is rotating with a constant angular velocity, and the vertical displacement d = 8.30cm for t = 0s. sketch two cycles of d as a function of t for the given values. The rotation is counterclockwise if that matters.

f = 3.20Hz

the form of the equation is d=R(cos/sin)wt.

im am able to find w = 2pi(f)= 20.106 or so and the form of the function is d=8.3____20.106. i just dont get how i know what function to use.

any help would be greatly appreciated as im being tested on this on Monday. Thanks

From your description, I gather that the point is at maximum at t = 0.

Which function (among sine and cosine) has a maximum at t=0?

 

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From your description, I gather that the point is at maximum at t = 0.

Which function (among sine and cosine) has a maximum at t=0?

well i know the answer is cosine but im just not sure why. in relation to x and y axis where t is the x axis is it saying when you are at 0 then y or(d)= 8.3? in that case i could see how cosine is used since a sine graph always starts at 0 on the y axis and cosine starts at its maximum or minimum.

 

[Deleted member 4993]

well i know the answer is cosine but im just not sure why. in relation to x and y axis where t is the x axis is it saying when you are at 0 then y or(d)= 8.3? .... Correct


in that case i could see how cosine is used since a sine graph always starts at 0 on the y axis and cosine starts at its maximum or minimum.

.

 

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ok think i got it now. thanks for the help