SOLUTION: : Given the points A (0,0), B (4,3) and C (2,9), what is the measure of angle< ABC? I've graphed it but I'm not sure on how to actually find the angle or length

Question 1037659: : Given the points A (0,0), B (4,3) and C (2,9), what is the measure of angle< ABC? I've graphed it but I'm not sure on how to actually find the angle or length
Answer by Alan3354(69443) (Show Source): You can put this solution on YOUR website!
Given the points A (0,0), B (4,3) and C (2,9), what is the measure of angle< ABC? I've graphed it but I'm not sure on how to actually find the angle or length
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1 way to do this is to find the 3 side lengths, then use the Cosine Law to find the angle.
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Another way is to use the Difference Formula for the tangents of 2 angles.
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Find the slope of side AB and BC.
The slope is the tangent of the angle between the line and the x-axis.

--> tan =
You can see from the graph that you use the negative tangent, ie, the angle is
> 90 degs.
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Wikipedia covers that well, look up "Half Angle Formulas"
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email via the TY note for help or to check your work.

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