# Calculating amplitudes, angular periods, trig style

#### 1slickVDC

Joined Dec 12, 2013
2
Okay. Finals week. The one chapter I was stuck at home sick is also one of the angriest. Would like some help working through these. If someone would be willing to give an answer or two and be procedural, I'd love you forever.

Example problems:

"Give amplitude and angular period for the following curves:

y = 5sin$$\theta$$ amp=____ ang. period=____

y = 3.519$$\theta$$ amp=____ ang. period=____"

Similar ones asking for peak, peak to peak, rms values (if given steps to gain one, I can obviously convert between them)

More with angular velocity, frequency and period (f & T I can calculate from each other also).

There's a couple other topics that are covered, but we'll get to those if I can't figure it out from what I get from this. Any help would be appreciated. Thanks!

#### shteii01

Joined Feb 19, 2010
4,644
Or.
Examples in the textbook.

#### 1slickVDC

Joined Dec 12, 2013
2
Couldnt find anything that even resembled what I was looking for on The Google, and the textbook really wasnt geared right for that class. Hence why Im asking here.

#### WBahn

Joined Mar 31, 2012
26,415
Okay. Finals week. The one chapter I was stuck at home sick is also one of the angriest. Would like some help working through these. If someone would be willing to give an answer or two and be procedural, I'd love you forever.

Example problems:

"Give amplitude and angular period for the following curves:

y = 5sin$$\theta$$ amp=____ ang. period=____

y = 3.519$$\theta$$ amp=____ ang. period=____"

Similar ones asking for peak, peak to peak, rms values (if given steps to gain one, I can obviously convert between them)

More with angular velocity, frequency and period (f & T I can calculate from each other also).

There's a couple other topics that are covered, but we'll get to those if I can't figure it out from what I get from this. Any help would be appreciated. Thanks!
You are basically asking for fundamental defining concepts.

If I tell you that the "amplitude" of a particular sinusoidal waveform is 120V, what does that tell you? If you had a plot of sinusoidal waveform on a set of axes that didn't have any scales on them, what values could you add to those scales as a result of knowing the amplitude?

For your second one, isn't that just a straight line with a slope of 3.519 ?

#### Papabravo

Joined Feb 24, 2006
18,781
There are no calculations. The answers are obvious by inspection.

• wayneh

#### WBahn

Joined Mar 31, 2012
26,415
There are no calculations. The answers are obvious by inspection.
Not for the second one. I suspect there is something left out from the post.

The problem is that they are obvious by inspection IF you understand the vocabulary used and how it maps to the mathematical functions. That's where the problem exists in this case and where the OP needs to focus. We can help him if he is willing to put in some effort, such as trying to answer the questions posed in Post #5.

#### Papabravo

Joined Feb 24, 2006
18,781
Not for the second one. I suspect there is something left out from the post.

The problem is that they are obvious by inspection IF you understand the vocabulary used and how it maps to the mathematical functions. That's where the problem exists in this case and where the OP needs to focus. We can help him if he is willing to put in some effort, such as trying to answer the questions posed in Post #5.
What is obvious in the second one is that it is not a periodic function and that the value of the function increases with the value of the independent variable θ. As you correctly pointed out, this may be a case of transcription error, because the question doesn't make much sense in this context, and I still didn't need any calculations. 