To solve this trigonometric equation, we can use the double angle formula for cosine which states that cos2x2x2x = 2cos^2xxx - 1.
Substitute this formula into the equation:
42cos2(x)−12cos^2(x) - 12cos2(x)−1 - 8cosxxx - 1 = 08cos^2xxx - 4 - 8cosxxx - 1 = 08cos^2xxx - 8cosxxx - 5 = 0
Now, let y = cosxxx. The equation becomes:
8y^2 - 8y - 5 = 0
Now we have a quadratic equation that we can solve using the quadratic formula:
y = 8±√(82−4<em>8</em>(−5))8 ± √(8^2 - 4<em>8</em>(-5))8±√(82−4<em>8</em>(−5)) / 2*8y = 8±√(64+160)8 ± √(64 + 160)8±√(64+160) / 16y = 8±√2248 ± √2248±√224 / 16
y = 8±14.978 ± 14.978±14.97 / 16
Now we solve for y:
y1 = 8+14.978 + 14.978+14.97 / 16 ≈ 1.187y2 = 8−14.978 - 14.978−14.97 / 16 ≈ -0.874
Since y = cosxxx, we can find the corresponding values of x:
x1 = cos^−1-1−11.1871.1871.187 is not validx2 = cos^−1-1−1−0.874-0.874−0.874 ≈ 2.610
Therefore, the solutions to the equation 4cos2x2x2x - 8cosxxx - 1 = 0 are x ≈ 2.610 + 2πn, n ∈ ℤ.
To solve this trigonometric equation, we can use the double angle formula for cosine which states that cos2x2x2x = 2cos^2xxx - 1.
Substitute this formula into the equation:
42cos2(x)−12cos^2(x) - 12cos2(x)−1 - 8cosxxx - 1 = 0
8cos^2xxx - 4 - 8cosxxx - 1 = 0
8cos^2xxx - 8cosxxx - 5 = 0
Now, let y = cosxxx. The equation becomes:
8y^2 - 8y - 5 = 0
Now we have a quadratic equation that we can solve using the quadratic formula:
y = 8±√(82−4<em>8</em>(−5))8 ± √(8^2 - 4<em>8</em>(-5))8±√(82−4<em>8</em>(−5)) / 2*8
y = 8±√(64+160)8 ± √(64 + 160)8±√(64+160) / 16
y = 8±√2248 ± √2248±√224 / 16
y = 8±14.978 ± 14.978±14.97 / 16
Now we solve for y:
y1 = 8+14.978 + 14.978+14.97 / 16 ≈ 1.187
y2 = 8−14.978 - 14.978−14.97 / 16 ≈ -0.874
Since y = cosxxx, we can find the corresponding values of x:
x1 = cos^−1-1−11.1871.1871.187 is not valid
x2 = cos^−1-1−1−0.874-0.874−0.874 ≈ 2.610
Therefore, the solutions to the equation 4cos2x2x2x - 8cosxxx - 1 = 0 are x ≈ 2.610 + 2πn, n ∈ ℤ.