If ` cos^(-1) a + cos^(-1) b + cos^(-1) c = pi` then prove that `a^2 + b^2 + c^2 + 2abc = 1.`

Prove the followings : If cos^(-1)a+cos^(-1)b+cos^(-1)c=pi then a^(2)+b^(2)+c^(2)+2abc=1 .

cos^(2)A+cos^(2)B+cos^(2)C=1-cos A cos B cos C prove that

If cos^(-1)a+cos^(-1)b+cos^(-1)c=pi, then the value of (a sqrt(1-a^(2))+b sqrt(1-b^(2))+c sqrt(1-c^(2))) will be

If A + B + C =pi , prove that : cos A + cos B - cos C> 1 .

If A+ B + C = pi, then cos^(2) A + cos ^(2) B + cos ^(2) C is equal to : A) 1 - cos A cos B cos C B) 1 - 2 cos A cos B cos C C) 2 cos A cos B cos C D) 1 + cos A cos B cos C

If A+B+C = pi , prove that : cos2A-cos2B -cos2C = -1+4cosAsinBsinC

If A+B+C = pi , prove that : cos2A-cos2B -cos2C = -1+4cosAsinBsinC

If in a ABC,cos^(2)A+cos^(2)B+cos^(2)C=1 prove that the triangle is right angled.

If A + B + C =pi , prove that : cos 2A + cos 2B -cos 2C= 1-4sin A sin B cos C .

If A + B + C =pi , prove that : cos 2A - cos 2B + cos 2C= 1-4 sin A cos B sin C .