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Solution 4.2:4b

From Förberedande kurs i matematik 1

Revision as of 13:05, 28 September 2008 by Ian (Talk | contribs)
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We start by subtracting 2 from 311, so that we get an angle between o and 2. This doesn't change the cosine value


cos311=cos311−2=cos35 


Then, by rewriting 35 as a sum of - and 2 -terms


35=33+23+21=+2+6

we see that 35 is an angle in the fourth quadrant which makes an angle 6 with the negative y -axis.


Image:4_2_4b1.gif

With the help of a triangle and a little trigonometry, we can determine the coordinates for the point on a unit circle which corresponds to the angle 35 .


Image:4_2_4_b2.gif

The point has coordinates 21−23  and cos311=cos35=21.

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