a →
· b →
= b →
· a
→
( k
a → )·
b → =
a → ·(
k b →
)=k(
a →
· b →
)
( a
→ + b
→ )·
c → =
a → ·
c → +
b → ·
c →
【導出計算】
a →
· b →
=|
a → ||
b →
|cosθ=|
b →
||
a → |cosθ=
b → ·
a →
(
k a →
)·
b →
=| k
a → ||
b →
|cosθ
=k|
a →
||
b → |cosθ
=|
a →
|| k
b → |cosθ
=
a → ·(
k b →
)
(
k a →
)·
b →
=| k
a → ||
b →
|cosθ
=k|
a →
||
b → |cosθ
=k(
a →
· b →
)
( a
→ + b
→ )·
c →
=|
a → +
b → ||
c →
|cosθ
=(
| a
→ + b
→ |cosθ
)|
c → |
=(
| a
→ |cosα+|
b →
|cosβ )|
c →
|
=|
a → ||
c →
|cosα+|
b →
||
c → |cosβ
=
a → ·
c → +
b → ·
c →
(右上図参照)
|