Answer:
Isolate the angle 2x, by following the reverse "order of operations".
Step-by-step explanation:
Explanation:
Step 1: Add 1 to both sides:
2
cos
2
(
2
x
)
=
1
Step 2: Divide both sides by 2:
cos
2
(
2
x
)
=
1
2
Step 3: Take the square root of both sides:
cos
(
2
x
)
=
√
2
2
or
cos
(
2
x
)
=
−
√
2
2
(don't forget the positive and negative solutions!)
Step 4: Use inverse of cosine to find the angles:
2
x
=
cos
−
1
(
√
2
2
)
or
2
x
=
cos
−
1
(
−
√
2
2
)
Step 5: Find angles that work:
2
x
=
π
4
or
2
x
=
7
π
4
or
2
x
=
3
π
4
or
2
x
=
5
π
4
Step 6: Solve for x:
x
=
π
8
,
7
π
8
,
3
π
8
,
5
π
8
or .785, 5.5, 2.36, 3.93
(decimal approximations are seen on the graph below)
