In the triangle ABC, the opposite sides of the angle are ABC. If bcosc + ccosb = 2acosa, vector AB * vector AC = 3 and B + C = 5, the value of a is obtained

In the triangle ABC, the opposite sides of the angle are ABC. If bcosc + ccosb = 2acosa, vector AB * vector AC = 3 and B + C = 5, the value of a is obtained


According to the sine theorem, sinbcosc + sinccosb = 2sinacosa
Sin (B + C) = sin (2a) = sin (π - a), a = 60 degree
Vector AB * vector AC = bccosa = 3, BC = 6
a^2=b^2+c^2-2bccosA=(b+c)^2-2bc-2bccosA=7
So, a = root 7

Elden Ring Premiere

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