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#171072 11/19/07 06:01 AM
Joined: Jun 2007
Posts: 20
A
Member
First I attempted to post this question in the technical forum but was rejected so I hope its ok that I place this here for now. I'm currently attempting to delve into a book called Alternating Current Fundamentals / Sixth Edition(Delmar Thomson Learning), I'm hoping someone might have some form of familiarity with this text.Chapter 1 Achievement review Question #5(If the rotating line of figure 1-8 has a length of one unit,determine its projection or shadow on the x & Y Axes at 30 degrees, 45 degrees, 120 degrees,and 240 degrees.)Refer to Fig. 1-8 and appendices 4&5. I simply don't get what is expected of me, in the whole question. Any help would be appreciated

Joined: Feb 2002
Posts: 183
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Member
Just guessing from your description:

You have 4 cases. In each case, there is a line of 1 unit long, one end at the origin (0,0) where the angle between the line and the x-axis is 30, 45, 120, and 240 degrees (one per case).

They want to know if you draw lines from the other end to the X and Y axes, where do they cross them?

The original line, the axis, and the projected line form a right triangle with the 1-unit line being the hypotenuse. The definitions of sine and cosine (sine = opposite/hypotenuse, cosine = adjacent/hypotenuse) will let you calculate the answer.

One thing to be careful of, most calculators expect the angles to be in radians, not degrees.

Joined: Dec 2003
Posts: 751
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I do believe the answer to the question is the shadow on the x-axis corresponds to a sine wave, and the shadow on the y-axis corresponds to a cosine wave.


Earl

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