Find vector c+ vector d|.
For the convenience of writing, the word "vector" is omitted below.
|c-d}^2=(c-d)^2.
=c^2-2cd+d^2.( 1)
|c+d|^2=c^2+2cd+d^2 ..
=c^2+2cd+d^2.(2)
(1)+(2), so:
(c-d}^2+|c+d|^2=2(c^2+d^2).
|c+d|^2=2(c^2+d^2)-(c-d)^2.
=2( 100+44 1)- 17^2.
= 1082-289.
=793.
∴|c+d|=√793.
| vector c+ vector d|=√793