jika panjang vektor u = 5, panjang vektor v =3, dan panjang vektor u+v = 7, maka panjang vektor u-v ?

|u| = 5
|v| = 3
|u + v| = 7

|u + v| = √|u|² + |v|² + 2|u||v|cos a
7 = √5² + 3² + 2|u||v|cos a
7² = 25 + 9 + 2|u||v|cos a
49 = 34 + 2|u||v|cos a
- 2|u||v|cos a = 34 - 49
- 2|u||v|cos a = -15
2|u||v|cos a = 15

|u - v| = √|u|² + |b|² - 2|a||b|cos a
= √5²+3² - 15
= √25 + 9 - 15
= √19