"find cos" <<<----- meaningless
you have all the sides of triangles ABC and ABR
so you can all those angles
e.g. in ABC
6^2 = 8^2 + 5^2 - 2(8)(5)cosB
80cosB = 64+25-36
cosB = 53/80
angle B = appr 48.5°
in the same way you can find angle BCA , etc
In ∆ABC, AB=8cm,BC=5cm and CA=6 cm. BC is produced to R,so that CR=3cm. Using cosine formula, find cos
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