What is the size of theta?

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1 Answer
F. Javier B.
Mar 5, 2018

Apply Cosine theorem

#a^2=b^2+c^2-2abc costheta#

Where a=5, b=4 and c=2

Explanation:

With this initial conditions

#costheta=(5^2-4^2-2^2)/(2·4·2)=5/16#

Thus we have #theta=arccos(5/16)#

Looking for it in tables, the nearest is 72º

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