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Byju's Answer
Standard XII
Mathematics
Projection Formula
cos 2a + cos ...
Question
cos 2a + cos 2b + cos 2c = -1 + k cos a cos b cos c. Find the value of k.
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Similar questions
Q.
What is z ,
△
A
B
C
cos
2
B
−
cos
2
C
b
+
c
+
cos
2
C
−
cos
2
A
c
+
a
+
cos
2
A
−
cos
2
B
a
+
b
=
z
Q.
Prove that:
cos
2
A
+
cos
2
B
+
cos
2
C
=
1
−
2
cos
A
cos
B
cos
C
.
Q.
In
Δ
A
B
C
prove:
cos
2
A
+
cos
2
B
+
cos
2
C
=
−
1
−
4
cos
A
cos
B
cos
C
Q.
Prove that,
cos
2
A
+
cos
2
B
−
cos
2
C
=
1
−
4
sin
A
sin
B
cos
C
.
Q.
If
A
+
B
+
C
=
π
, then prove that
cos
2
A
+
cos
2
B
+
cos
2
C
=
−
1
−
4
cos
A
cos
B
cos
C
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