If the edges of a rectangular parallelepiped are `a ,b ,c` prove that the angles between the four diagonals are given by `cos^(-1)((a^2+-b^2+-c^2)/(a^2+b^2+c^2))dot`

In A B C , prove that (a-b^2cos^2C/2+(a+b)^2sin^2C/2=c^2dot

In A B C , prove that (a-b)^2cos^2C/2+(a+b)^2sin^2C/2=c^2dot

If A, B, C are the angles of a right angled triangle, then (cos^2A+ cos^2B+ cos^2C) equals

In triangle A B C ,a , b , c are the lengths of its sides and A , B ,C are the angles of triangle A B Cdot The correct relation is given by (a) (b-c)sin((B-C)/2)=acosA/2 (b) (b-c)cos(A/2)=asin((B-C)/2) (c) (b+c)sin((B+C)/2)=acosA/2 (d) (b-c)cos(A/2)=2asin(B+C)/2

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

In any Delta A B C , prove that: (cos A)/a+(cos B)/b+(cos C)/c=(a^2+b^2+c^2)/(2a b c)

A rectangular parallelepiped is formed by planes drawn through the points (5, 7, 9) and (2, 3, 7) parallel to the coordinate planes. The length of an edge of this rectangular parallelepiped is a. 2 b. 3 c. 4 d. all of these

If a, b and c are in G.P. then prove that 1 a 2 - b 2 + 1 b 2 = 1 b 2 - c 2 . 1/(a^2-b^2)+1/(b^2)=1/(b^2-c^2)dot

Prove that (cos^(2)A-sin^(2)B)+1-cos^(2)C

In any triangle A B C , prove that: (1+cos(A-B)cos C)/(1+cos(A-C)cos B)=(a^2+b^2)/(a^2+c^2)