Homework Help: math

Posted by donovan on Thursday, July 26, 2012 at 10:09pm.

given the points A(0,0) ,B(4,3),C(2,9) what is the measure of < ABC?

math - Reiny, Thursday, July 26, 2012 at 11:29pm
let a=BC
b = AC
c = AB

find the length of each of the sides a, b, and c
the use the cosine law.
b^2 = a^2 + c^2 - 2ac cos B
solve for angle B

I will do one of the lengths,
a= √((2-4)^2 + 9-3)^2 ) = √(4+36) = √40
math - donovan, Friday, July 27, 2012 at 5:27pm
so would

b=the square root of 85 ?

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