Tips och lösning till övning 3.1
SamverkanLinalgLIU
(Skillnad mellan versioner)
Rad 5: | Rad 5: | ||
<math>|\boldsymbol{u}|^2=\boldsymbol{u}\cdot | <math>|\boldsymbol{u}|^2=\boldsymbol{u}\cdot | ||
- | \boldsymbol{u} | + | \boldsymbol{u}</math> |
{{NAVCONTENT_STEP}} | {{NAVCONTENT_STEP}} | ||
'''Tips 2''' | '''Tips 2''' | ||
- | + | Byt <math>\boldsymbol{u}</math> mot <math>\boldsymbol{u}-\boldsymbol{v}</math> under tips 1 | |
{{NAVCONTENT_STEP}} | {{NAVCONTENT_STEP}} | ||
'''Tips 3''' | '''Tips 3''' | ||
- | + | <math>5^2=|\boldsymbol{u}-\boldsymbol{v}|^2</math> | |
{{NAVCONTENT_STEP}} | {{NAVCONTENT_STEP}} | ||
'''Lösning''' | '''Lösning''' |
Nuvarande version
Tips 1
Använd resultatet
\displaystyle |\boldsymbol{u}|^2=\boldsymbol{u}\cdot \boldsymbol{u}
Tips 2
Byt \displaystyle \boldsymbol{u} mot \displaystyle \boldsymbol{u}-\boldsymbol{v} under tips 1
Tips 3
\displaystyle 5^2=|\boldsymbol{u}-\boldsymbol{v}|^2
Lösning
Vi har att
(\boldsymbol{u}-\boldsymbol{v})=|\boldsymbol{u}|^2+|\boldsymbol{v}|^2-2\boldsymbol{u}\cdot\boldsymbol{v}=3^2+4^2-2\boldsymbol{u}\cdot\boldsymbol{v},
dvs \displaystyle \boldsymbol{u}\cdot\boldsymbol{v}=0.