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Popular >

2(1-cos^2(x))= 3/2

Solution

2 (1 - cos^{2} (x)) = \frac{3}{2}

Solution

x = \frac{π}{3} + 2 πn, x = \frac{5 π}{3} + 2 πn, x = \frac{2 π}{3} + 2 πn, x = \frac{4 π}{3} + 2 πn

Degrees

x = 6 0^{\circ} + 36 0^{\circ} n, x = 30 0^{\circ} + 36 0^{\circ} n, x = 12 0^{\circ} + 36 0^{\circ} n, x = 24 0^{\circ} + 36 0^{\circ} n

Solution steps

2 (1 - cos^{2} (x)) = \frac{3}{2}

Solve by substitution

2 (1 - cos^{2} (x)) = \frac{3}{2}

Let:

cos (x) = u

2 (1 - u^{2}) = \frac{3}{2}

2 (1 - u^{2}) = \frac{3}{2} : u = \frac{1}{2}, u = - \frac{1}{2}

2 (1 - u^{2}) = \frac{3}{2}

Divide both sides by

2

2 (1 - u^{2}) = \frac{3}{2}

Divide both sides by

2

\frac{2 ( 1 - u ^{2} )}{2} = \frac{\frac{3}{2}}{2}

Simplify

\frac{2 ( 1 - u ^{2} )}{2} = \frac{\frac{3}{2}}{2}

Simplify

\frac{2 ( 1 - u ^{2} )}{2} : 1 - u^{2}

\frac{2 ( 1 - u ^{2} )}{2}

Divide the numbers:

\frac{2}{2} = 1

= 1 - u^{2}

Simplify

\frac{\frac{3}{2}}{2} : \frac{3}{4}

\frac{\frac{3}{2}}{2}

Apply the fraction rule:

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

= \frac{3}{2 \cdot 2}

Multiply the numbers:

2 \cdot 2 = 4

= \frac{3}{4}

1 - u^{2} = \frac{3}{4}

1 - u^{2} = \frac{3}{4}

1 - u^{2} = \frac{3}{4}

Move

1

to the right side

1 - u^{2} = \frac{3}{4}

Subtract

1

from both sides

1 - u^{2} - 1 = \frac{3}{4} - 1

Simplify

1 - u^{2} - 1 = \frac{3}{4} - 1

Simplify

1 - u^{2} - 1 : - u^{2}

1 - u^{2} - 1

Add similar elements:

1 - 1 = 0

= - u^{2}

Simplify

\frac{3}{4} - 1 : - \frac{1}{4}

\frac{3}{4} - 1

Convert element to fraction:

1 = \frac{1 \cdot 4}{4}

= - \frac{1 \cdot 4}{4} + \frac{3}{4}

Since the denominators are equal, combine the fractions:

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

= \frac{- 1 \cdot 4 + 3}{4}

- 1 \cdot 4 + 3 = - 1

- 1 \cdot 4 + 3

Multiply the numbers:

1 \cdot 4 = 4

= - 4 + 3

Add/Subtract the numbers:

- 4 + 3 = - 1

= - 1

= \frac{- 1}{4}

Apply the fraction rule:

\frac{- a}{b} = - \frac{a}{b}

= - \frac{1}{4}

- u^{2} = - \frac{1}{4}

- u^{2} = - \frac{1}{4}

- u^{2} = - \frac{1}{4}

Divide both sides by

- 1

- u^{2} = - \frac{1}{4}

Divide both sides by

- 1

\frac{- u ^{2}}{- 1} = \frac{- \frac{1}{4}}{- 1}

Simplify

\frac{- u ^{2}}{- 1} = \frac{- \frac{1}{4}}{- 1}

Simplify

\frac{- u ^{2}}{- 1} : u^{2}

\frac{- u ^{2}}{- 1}

Apply the fraction rule:

\frac{- a}{- b} = \frac{a}{b}

= \frac{u ^{2}}{1}

Apply rule

\frac{a}{1} = a

= u^{2}

Simplify

\frac{- \frac{1}{4}}{- 1} : \frac{1}{4}

\frac{- \frac{1}{4}}{- 1}

Apply the fraction rule:

\frac{- a}{- b} = \frac{a}{b}

= \frac{\frac{1}{4}}{1}

Apply the fraction rule:

\frac{a}{1} = a

= \frac{1}{4}

u^{2} = \frac{1}{4}

u^{2} = \frac{1}{4}

u^{2} = \frac{1}{4}

For

x^{2} = f (a)

the solutions are

x = f (a), - f (a)

u = \frac{1}{4}, u = - \frac{1}{4}

\frac{1}{4} = \frac{1}{2}

\frac{1}{4}

Apply radical rule:

assuming

a \geq 0, b \geq 0

= \frac{1}{4}

4 = 2

4

Factor the number:

4 = 2^{2}

= 2^{2}

Apply radical rule:

2^{2} = 2

= 2

= \frac{1}{2}

Apply rule

1 = 1

= \frac{1}{2}

- \frac{1}{4} = - \frac{1}{2}

- \frac{1}{4}

Simplify

\frac{1}{4} : \frac{1}{2}

\frac{1}{4}

Apply radical rule:

assuming

a \geq 0, b \geq 0

= \frac{1}{4}

4 = 2

4

Factor the number:

4 = 2^{2}

= 2^{2}

Apply radical rule:

2^{2} = 2

= 2

= \frac{1}{2}

= - \frac{1}{2}

Apply rule

1 = 1

= - \frac{1}{2}

u = \frac{1}{2}, u = - \frac{1}{2}

Substitute back

u = cos (x)

cos (x) = \frac{1}{2}, cos (x) = - \frac{1}{2}

cos (x) = \frac{1}{2}, cos (x) = - \frac{1}{2}

cos (x) = \frac{1}{2} : x = \frac{π}{3} + 2 πn, x = \frac{5 π}{3} + 2 πn

cos (x) = \frac{1}{2}

General solutions for

cos (x) = \frac{1}{2}

cos (x)

periodicity table with

2 πn

cycle:

x 0 \frac{π}{6} \frac{π}{4} \frac{π}{3} \frac{π}{2} \frac{2 π}{3} \frac{3 π}{4} \frac{5 π}{6} cos (x) 1 \frac{3}{2} \frac{2}{2} \frac{1}{2} 0 - \frac{1}{2} - \frac{2}{2} - \frac{3}{2} x π \frac{7 π}{6} \frac{5 π}{4} \frac{4 π}{3} \frac{3 π}{2} \frac{5 π}{3} \frac{7 π}{4} \frac{11 π}{6} cos (x) - 1 - \frac{3}{2} - \frac{2}{2} - \frac{1}{2} 0 \frac{1}{2} \frac{2}{2} \frac{3}{2}

x = \frac{π}{3} + 2 πn, x = \frac{5 π}{3} + 2 πn

x = \frac{π}{3} + 2 πn, x = \frac{5 π}{3} + 2 πn

cos (x) = - \frac{1}{2} : x = \frac{2 π}{3} + 2 πn, x = \frac{4 π}{3} + 2 πn

cos (x) = - \frac{1}{2}

General solutions for

cos (x) = - \frac{1}{2}

cos (x)

periodicity table with

2 πn

cycle:

x 0 \frac{π}{6} \frac{π}{4} \frac{π}{3} \frac{π}{2} \frac{2 π}{3} \frac{3 π}{4} \frac{5 π}{6} cos (x) 1 \frac{3}{2} \frac{2}{2} \frac{1}{2} 0 - \frac{1}{2} - \frac{2}{2} - \frac{3}{2} x π \frac{7 π}{6} \frac{5 π}{4} \frac{4 π}{3} \frac{3 π}{2} \frac{5 π}{3} \frac{7 π}{4} \frac{11 π}{6} cos (x) - 1 - \frac{3}{2} - \frac{2}{2} - \frac{1}{2} 0 \frac{1}{2} \frac{2}{2} \frac{3}{2}

x = \frac{2 π}{3} + 2 πn, x = \frac{4 π}{3} + 2 πn

x = \frac{2 π}{3} + 2 πn, x = \frac{4 π}{3} + 2 πn

Combine all the solutions

x = \frac{π}{3} + 2 πn, x = \frac{5 π}{3} + 2 πn, x = \frac{2 π}{3} + 2 πn, x = \frac{4 π}{3} + 2 πn

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