The sides of satisfy

MATHEMATICS · Multi correct · IB Diploma Programme · Mathematics: Analysis and Approaches · Geometry and Trigonometry · Geometry and Trigonometry

Problem

The sides of △ABC\triangle ABC satisfy 2a2+4b2+c2=4ab+2ac2a^2+4b^2+c^2=4ab+2ac. Then: (1) The triangle is isosceles. (2) The triangle is obtuse. (3) B=cos⁡−1(78)B=\cos^{-1}\left(\frac{7}{8}\right). (4) A=cos⁡−1(14)A=\cos^{-1}\left(\frac{1}{4}\right).

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