A regular tetrahedron has 4 faces which are equilateral triangles. In the figure below, PQRS represents a regular tetrahedron. N and M are mid-points of RS and PQ respectively such that NM ⊥ PQ and NM ⊥ RS. Let s be the length of each edge of the solid. Find the length of NM in terms of s:
Answers
Answer:
Correct option is
A
5
2
Area of ΔBCD=
2
1
∣
∣
∣
∣
BC
×
BD
∣
∣
∣
∣
=
2
1
∣
∣
∣
∣
(b
i
^
−c
j
^
)×(b
i
^
−d
k
^
)
∣
∣
∣
∣
=
2
1
∣
∣
∣
∣
bd
j
^
+bc
k
^
+dc
i
^
∣
∣
∣
∣
=
2
1
b
2
c
2
+c
2
d
2
+d
2
b
2
...(1)
Now,
6=bc;8=cd;10=bd (Given)
b
2
c
2
+c
2
d
2
+d
2
b
2
=200
Substituting the value in (1), we get
A=
2
1
200
=5
2
Hence, option A.
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Answer:
4 terms च्या साहित्याचा कर्ता अने
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