(a+b+c)^(2)-(a-b-c)^(2)=

(cos ^(2) ((B-C)/( 2)) )/( (b+c)^(2))+( sin ^(2)((B-C)/( 2)) )/( (b-c)^(2))=

(cos^(2)((B-C)/(2)))/((b+c)^(2))+(sin^(2)((B-C)/(2)))/((b-c)^(2))=(1)/(a^(2))

|(a,b+c,a^(2)),(b,c+a,b^(2)),(c,a+b,c^(2))|=

If Delta ABC is such that angle A = 90 ^(@) , angle B ne angle C " then " ( b^(2) + c^(2))/( b^(2) - c^(2)) sin ( B- C) =

(c) If (a)/(b)=(b)/(c) ,prove that (a+b+c)(a-b+c)=a^(2)+b^(2)+c^(2)

If a, b, c are in continued proportion, prove that (a+b+c)(a-b+c)=a^(2)+b^(2)+c^(2) .

Prove: |(a^2,a^2-(b-c)^2,b c), (b^2,b^2-(c-a)^2,c a),( c^2,c^2-(a-b)^2,a b)|=(a-b)(b-c)(c-a)(a+b+c)(a^2+b^2+c^2)

Prove that |a b+c a^2b c+a b^2c a+b c^2|=-(a+b+c)xx(a-b)(b-c)(c-a)dot