A parallelogram is fromed with`veca` and `vecb` as the sides let `vecd_(1)` and `vecd_(2)` be the diagonals of the parallelogram , them `a^(2) +b^(2)=`

Options

A. `A^(2) + B^(2)`
B. `(A^(2) - B^(2))/(2)`
C. `(A^(2) + B^(2))/(2)`
D. `2(A^(2) + B^(2))`

Answer

D

Explanation

`" "D_(1)^(2) = A^(2) + B^(2) + 2AB cos theta`
`" "D_(2)^(2) = A^(2) + B^(2) - 2AB cos theta`