题目内容
如下图,在长方体ABCD—A1B1C1D1中,![]()
证明:
=![]()
=
(
)=
(
+
)=
(a+b),
=![]()
=
(
+
=
(-
-
)=
(-a-c),
=![]()
=
(
+
)=
(-
+
)=
(-b+c),
∴
+
+
=
(a+b-a-c-b+c)=0.
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题目内容
如下图,在长方体ABCD—A1B1C1D1中,![]()
证明:
=![]()
=
(
)=
(
+
)=
(a+b),
=![]()
=
(
+
=
(-
-
)=
(-a-c),
=![]()
=
(
+
)=
(-
+
)=
(-b+c),
∴
+
+
=
(a+b-a-c-b+c)=0.