SOLUTION: given the triangle whose vertices are at a(2,0), b(-7,-8) and c(-2,-7). Find the interior angle at vertex A and vetrex C.

Algebra ->  Length-and-distance -> SOLUTION: given the triangle whose vertices are at a(2,0), b(-7,-8) and c(-2,-7). Find the interior angle at vertex A and vetrex C.      Log On


   

Question 1165028: given the triangle whose vertices are at a(2,0), b(-7,-8) and c(-2,-7). Find the interior angle at vertex A and vetrex C.
Answer by Alan3354(69443) About Me  (Show Source):
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given the triangle whose vertices are at a(2,0), b(-7,-8) and c(-2,-7). Find the interior angle at vertex A and vetrex C.
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Find the lengths of the sides, then use the Cosine Law to find one of the angles, then the Law of Sines to find a 2nd angle.
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Or,
Find the slopes of the 3 sides.
The slope is the tangent of the side wrt to the x-axis.
Slope of AB = -8/-9 = 8/9
Angle = atan(8/9) =~ 41.633 degs (wrt to the positive x-axis)
Slope of AC = -7/-4 = 7/4
Angle =~ 60.255 degs
---> angle A = 18.622 degs