Answer:
Step-by-step explanation:
L
H
S
=
cos
4
x
=
2
cos
2
(
2
x
)
−
1
=
2
(
cos
(
2
x
)
)
2
−
1
=
2
(
2
cos
2
x
−
1
)
2
−
1
=
2
(
4
cos
4
x
−
4
cos
2
x
+
1
)
−
1
=
8
cos
4
x
−
8
cos
2
x
+
2
−
1
=
8
cos
4
x
−
8
cos
2
x
+
1
=
R
H
S
Again
L
H
S
=
cos
4
x
=
2
cos
2
(
2
x
)
−
1
=
2
(
1
−
2
sin
2
x
)
)
2
−
1
=
2
(
1
−
4
sin
2
x
+
4
sin
4
x
)
−
1
=
2
−
8
sin
2
x
+
8
sin
4
x
−
1
=
8
sin
4
x
−
8
sin
2
x
+
1
=
R
H
S
sin
2
x
+
cos
2
x
=
1
cos
2
x
=
1
−
sin
2
x
substitute in the equation as follows
8
cos
4
x
−
8
cos
2
x
+
1
=
8
cos
2
x
(
cos
2
x
−
1
)
+
1
=
8
(
1
−
sin
2
x
)
(
1
−
sin
2
x
−
1
)
+
1
=
8
(
1
−
sin
2
x
)
(
−
sin
2
x
)
+
1
=
8
sin
4
x
−
8
sin
2
x
+
1
Answer:
Line B - red line
Step-by-step explanation:
