cos4θ=?
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Answers
Answered by
0
Step-by-step explanation:
Using:
cos
2
θ
=
cos
2
θ
−
sin
2
θ
cos
2
θ
+
sin
2
θ
=
1
So:
cos
2
θ
=
cos
2
θ
−
sin
2
θ
=
cos
2
θ
−
(
1
−
cos
2
θ
)
=
2
cos
2
θ
−
1
So:
cos
4
θ
=
2
cos
2
2
θ
−
1
cos
4
θ
=
2
(
2
cos
2
θ
−
1
)
2
−
1
cos
4
θ
=
2
(
4
cos
4
θ
−
4
cos
2
θ
+
1
)
−
1
cos
4
θ
=
8
cos
4
θ
−
8
cos
2
θ
+
1
Answered by
0
0.66693806165 radians
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