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Popular >

cos^2(2x)>(2sqrt(3))/4

Solution

cos^{2} (2 x) > \frac{2 3}{4}

Solution

- \frac{arccos ( \frac{3}{2} )}{2} + πn < x < \frac{arccos ( \frac{3}{2} )}{2} + πn or \frac{arccos ( - \frac{3}{2} )}{2} + πn < x < \frac{2 π - arccos ( - \frac{3}{2} )}{2} + πn

Interval Notation

- \frac{arccos ( \frac{3}{2} )}{2} + πn, \frac{arccos ( \frac{3}{2} )}{2} + πn \cup \frac{arccos ( - \frac{3}{2} )}{2} + πn, \frac{2 π - arccos ( - \frac{3}{2} )}{2} + πn

Decimal Notation

- 0.18736 \dots + πn < x < 0.18736 \dots + πn or 1.38342 \dots + πn < x < 1.75816 \dots + πn

Solution steps

cos^{2} (2 x) > \frac{2 3}{4}

For

u^{n} > a

, if

n

is even then

cos (2 x) < - \frac{2 3}{4} or cos (2 x) > \frac{2 3}{4}

\frac{2 3}{4} = \frac{3}{2}

\frac{2 3}{4}

\frac{2 3}{4} = \frac{3}{2}

\frac{2 3}{4}

Cancel the common factor:

2

= \frac{3}{2}

= \frac{3}{2}

cos (2 x) < - \frac{3}{2} or cos (2 x) > \frac{3}{2}

cos (2 x) < - \frac{3}{2} : \frac{arccos ( - \frac{3}{2} )}{2} + πn < x < \frac{2 π - arccos ( - \frac{3}{2} )}{2} + πn

cos (2 x) < - \frac{3}{2}

For

cos (x) < a

, if

- 1 < a \leq 1

then

arccos (a) + 2 πn < x < 2 π - arccos (a) + 2 πn

arccos - \frac{3}{2} + 2 πn < 2 x < 2 π - arccos - \frac{3}{2} + 2 πn

a < u < b

then

a < u and u < b

arccos - \frac{3}{2} + 2 πn < 2 x and 2 x < 2 π - arccos - \frac{3}{2} + 2 πn

arccos - \frac{3}{2} + 2 πn < 2 x : x > \frac{arccos ( - \frac{3}{2} )}{2} + πn

arccos - \frac{3}{2} + 2 πn < 2 x

Switch sides

2 x > arccos - \frac{3}{2} + 2 πn

Divide both sides by

2

2 x > arccos - \frac{3}{2} + 2 πn

Divide both sides by

2

\frac{2 x}{2} > \frac{arccos ( - \frac{3}{2} )}{2} + \frac{2 πn}{2}

Simplify

x > \frac{arccos ( - \frac{3}{2} )}{2} + πn

x > \frac{arccos ( - \frac{3}{2} )}{2} + πn

2 x < 2 π - arccos - \frac{3}{2} + 2 πn : x < \frac{2 π - arccos ( - \frac{3}{2} )}{2} + πn

2 x < 2 π - arccos - \frac{3}{2} + 2 πn

Divide both sides by

2

2 x < 2 π - arccos - \frac{3}{2} + 2 πn

Divide both sides by

2

\frac{2 x}{2} < \frac{2 π}{2} - \frac{arccos ( - \frac{3}{2} )}{2} + \frac{2 πn}{2}

Simplify

x < π - \frac{arccos ( - \frac{3}{2} )}{2} + πn

Simplify

π - \frac{arccos ( - \frac{3}{2} )}{2} : \frac{2 π - arccos ( - \frac{3}{2} )}{2}

π - \frac{arccos ( - \frac{3}{2} )}{2}

Convert element to fraction:

π = \frac{π 2}{2}

= \frac{π 2}{2} - \frac{arccos ( - \frac{3}{2} )}{2}

Since the denominators are equal, combine the fractions:

\frac{a}{c} \pm \frac{b}{c} = \frac{a \pm b}{c}

= \frac{π 2 - arccos ( - \frac{3}{2} )}{2}

x < \frac{2 π - arccos ( - \frac{3}{2} )}{2} + πn

x < \frac{2 π - arccos ( - \frac{3}{2} )}{2} + πn

Combine the intervals

x > \frac{arccos ( - \frac{3}{2} )}{2} + πn and x < \frac{2 π - arccos ( - \frac{3}{2} )}{2} + πn

Merge Overlapping Intervals

\frac{arccos ( - \frac{3}{2} )}{2} + πn < x < \frac{2 π - arccos ( - \frac{3}{2} )}{2} + πn

cos (2 x) > \frac{3}{2} : - \frac{arccos ( \frac{3}{2} )}{2} + πn < x < \frac{arccos ( \frac{3}{2} )}{2} + πn

cos (2 x) > \frac{3}{2}

For

cos (x) > a

, if

- 1 \leq a < 1

then

- arccos (a) + 2 πn < x < arccos (a) + 2 πn

- arccos \frac{3}{2} + 2 πn < 2 x < arccos \frac{3}{2} + 2 πn

a < u < b

then

a < u and u < b

- arccos \frac{3}{2} + 2 πn < 2 x and 2 x < arccos \frac{3}{2} + 2 πn

- arccos \frac{3}{2} + 2 πn < 2 x : x > - \frac{arccos ( \frac{3}{2} )}{2} + πn

- arccos \frac{3}{2} + 2 πn < 2 x

Switch sides

2 x > - arccos \frac{3}{2} + 2 πn

Divide both sides by

2

2 x > - arccos \frac{3}{2} + 2 πn

Divide both sides by

2

\frac{2 x}{2} > - \frac{arccos ( \frac{3}{2} )}{2} + \frac{2 πn}{2}

Simplify

x > - \frac{arccos ( \frac{3}{2} )}{2} + πn

x > - \frac{arccos ( \frac{3}{2} )}{2} + πn

2 x < arccos \frac{3}{2} + 2 πn : x < \frac{arccos ( \frac{3}{2} )}{2} + πn

2 x < arccos \frac{3}{2} + 2 πn

Divide both sides by

2

2 x < arccos \frac{3}{2} + 2 πn

Divide both sides by

2

\frac{2 x}{2} < \frac{arccos ( \frac{3}{2} )}{2} + \frac{2 πn}{2}

Simplify

x < \frac{arccos ( \frac{3}{2} )}{2} + πn

x < \frac{arccos ( \frac{3}{2} )}{2} + πn

Combine the intervals

x > - \frac{arccos ( \frac{3}{2} )}{2} + πn and x < \frac{arccos ( \frac{3}{2} )}{2} + πn

Merge Overlapping Intervals

- \frac{arccos ( \frac{3}{2} )}{2} + πn < x < \frac{arccos ( \frac{3}{2} )}{2} + πn

Combine the intervals

\frac{arccos ( - \frac{3}{2} )}{2} + πn < x < \frac{2 π - arccos ( - \frac{3}{2} )}{2} + πn or - \frac{arccos ( \frac{3}{2} )}{2} + πn < x < \frac{arccos ( \frac{3}{2} )}{2} + πn

Merge Overlapping Intervals

- \frac{arccos ( \frac{3}{2} )}{2} + πn < x < \frac{arccos ( \frac{3}{2} )}{2} + πn or \frac{arccos ( - \frac{3}{2} )}{2} + πn < x < \frac{2 π - arccos ( - \frac{3}{2} )}{2} + πn

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