a |
b |
a |
b |
a |
a |
b |
A.30° | B.45° | C.60° | D.90° |
a |
b |
a |
a |
a |
b |
2 |
a |
b |
a |
b |
| ||
2 |
a |
b |
a |
b |
c |
a |
b |
a |
c |
AB |
AC |
AB |
AC |
A.arccos(-
| B.
| ||||||
C.arccos
| D.
|
a |
2 |
b |
a |
b |
a |
b |
a |
b |
a |
3 |
b |
a |
b |
a |
b |
a |
b |
a |
b) |
a |
b |
a |
b |
a |
a |
b |
a |
b |
a |
b |
a |
a |
b |
A.45° | B.60° | C.120° | D.135° |
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