Saturday, October 26, 2013

How to determine the side a of triangle ABC if i know the angle A= 60 degrees and the sides b=square root 3 c=2?

We'll have to use the law of cosines to determine the
length of the side "a".


a^2 = b^2 + c^2 - 2b*c*cos (b,c)
(1)


We know that the side "a" is facing to the angle A,
then the side "b" is facing to B and the side "c" is facing to the angle
C.


The angle enclosed by the sides "b" and "c" is
A.


We know, from enunciation, that A=60
degrees.


Then cos 60 =
1/2


We'll substitute the values of b and c and the cosine
of A, into the relation (1).


a^2 = 3 + 4 -
2*sqrt3*2/2


a^2 = 7 - 2sqrt3


a
= sqrt(7 - 2sqrt3)


The length of the side "a"
is: a = a = sqrt(7 - 2sqrt3).

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