9. If in a triangle ABC, cos A cosB + sin A sin B Sin C...

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9. If in a triangle ABC, cos A cosB + sin A sin B Sin³ C = 1, then, with usual notation in AABC, a) the triangle is isosceles b) the triangle is right angled c) R:r=(V2+1):1 d) =1:1:(2+1) 9. If in a triangle ABC, cos A cosB + sin A sin B Sin³ C = 1, then, with usual notation in AABC, a) the triangle is isosceles b) the triangle is right angled c) R:r=(V2+1):1 d) =1:1:(2+1)