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Popular >

-sin(x)(2+sin(x))-cos^2(x)>0

Solution

- sin (x) (2 + sin (x)) - cos^{2} (x) > 0

Solution

- \frac{5 π}{6} + 2 πn < x < - \frac{π}{6} + 2 πn

Interval Notation

(- \frac{5 π}{6} + 2 πn, - \frac{π}{6} + 2 πn)

Decimal Notation

- 2.61799 \dots + 2 πn < x < - 0.52359 \dots + 2 πn

Solution steps

- sin (x) (2 + sin (x)) - cos^{2} (x) > 0

Use the following identity:

cos^{2} (x) + sin^{2} (x) = 1

Therefore

cos^{2} (x) = 1 - sin^{2} (x)

- sin (x) (2 + sin (x)) - (1 - sin^{2} (x)) > 0

Simplify

- sin (x) (2 + sin (x)) - (1 - sin^{2} (x)) : - 2 sin (x) - 1

- sin (x) (2 + sin (x)) - (1 - sin^{2} (x))

Expand

- sin (x) (2 + sin (x)) : - 2 sin (x) - sin^{2} (x)

- sin (x) (2 + sin (x))

Apply the distributive law:

a (b + c) = ab + a c

a = - sin (x), b = 2, c = sin (x)

= - sin (x) \cdot 2 + (- sin (x)) sin (x)

Apply minus-plus rules

+ (- a) = - a

= - 2 sin (x) - sin (x) sin (x)

sin (x) sin (x) = sin^{2} (x)

sin (x) sin (x)

Apply exponent rule:

a^{b} \cdot a^{c} = a^{b + c}

sin (x) sin (x) = sin^{1 + 1} (x)

= sin^{1 + 1} (x)

Add the numbers:

1 + 1 = 2

= sin^{2} (x)

= - 2 sin (x) - sin^{2} (x)

= - 2 sin (x) - sin^{2} (x) - (1 - sin^{2} (x))

- (1 - sin^{2} (x)) : - 1 + sin^{2} (x)

- (1 - sin^{2} (x))

Distribute parentheses

= - (1) - (- sin^{2} (x))

Apply minus-plus rules

- (- a) = a, - (a) = - a

= - 1 + sin^{2} (x)

= - 2 sin (x) - sin^{2} (x) - 1 + sin^{2} (x)

Simplify

- 2 sin (x) - sin^{2} (x) - 1 + sin^{2} (x) : - 2 sin (x) - 1

- 2 sin (x) - sin^{2} (x) - 1 + sin^{2} (x)

Group like terms

= - 2 sin (x) - sin^{2} (x) + sin^{2} (x) - 1

Add similar elements:

- sin^{2} (x) + sin^{2} (x) = 0

= - 2 sin (x) - 1

= - 2 sin (x) - 1

- 2 sin (x) - 1 > 0

Move

1

to the right side

- 2 sin (x) - 1 > 0

Add

1

to both sides

- 2 sin (x) - 1 + 1 > 0 + 1

Simplify

- 2 sin (x) > 1

- 2 sin (x) > 1

Multiply both sides by

- 1

- 2 sin (x) > 1

Multiply both sides by -1 (reverse the inequality)

(- 2 sin (x)) (- 1) < 1 \cdot (- 1)

Simplify

2 sin (x) < - 1

2 sin (x) < - 1

Divide both sides by

2

2 sin (x) < - 1

Divide both sides by

2

\frac{2 sin ( x )}{2} < \frac{- 1}{2}

Simplify

sin (x) < - \frac{1}{2}

sin (x) < - \frac{1}{2}

For

sin (x) < a

, if

- 1 < a \leq 1

then

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

- π - arcsin (- \frac{1}{2}) + 2 πn < x < arcsin (- \frac{1}{2}) + 2 πn

Simplify

- π - arcsin (- \frac{1}{2}) : - \frac{5 π}{6}

- π - arcsin (- \frac{1}{2})

arcsin (- \frac{1}{2}) = - \frac{π}{6}

arcsin (- \frac{1}{2})

Use the following property:

arcsin (- x) = - arcsin (x)

arcsin (- \frac{1}{2}) = - arcsin (\frac{1}{2})

= - arcsin (\frac{1}{2})

Use the following trivial identity:

arcsin (\frac{1}{2}) = \frac{π}{6}

arcsin (\frac{1}{2})

x 0 \frac{1}{2} \frac{2}{2} \frac{3}{2} 1 arcsin (x) 0 \frac{π}{6} \frac{π}{4} \frac{π}{3} \frac{π}{2} arcsin (x) 0^{\circ} 3 0^{\circ} 4 5^{\circ} 6 0^{\circ} 9 0^{\circ}

= \frac{π}{6}

= - \frac{π}{6}

= - π - (- \frac{π}{6})

Simplify

- π - (- \frac{π}{6})

Apply rule

- (- a) = a

= - π + \frac{π}{6}

Convert element to fraction:

π = \frac{π 6}{6}

= - \frac{π 6}{6} + \frac{π}{6}

Since the denominators are equal, combine the fractions:

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

= \frac{- π 6 + π}{6}

Add similar elements:

- 6 π + π = - 5 π

= \frac{- 5 π}{6}

Apply the fraction rule:

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

= - \frac{5 π}{6}

= - \frac{5 π}{6}

Simplify

arcsin (- \frac{1}{2}) : - \frac{π}{6}

arcsin (- \frac{1}{2})

Use the following property:

arcsin (- x) = - arcsin (x)

arcsin (- \frac{1}{2}) = - arcsin (\frac{1}{2})

= - arcsin (\frac{1}{2})

Use the following trivial identity:

arcsin (\frac{1}{2}) = \frac{π}{6}

arcsin (\frac{1}{2})

x 0 \frac{1}{2} \frac{2}{2} \frac{3}{2} 1 arcsin (x) 0 \frac{π}{6} \frac{π}{4} \frac{π}{3} \frac{π}{2} arcsin (x) 0^{\circ} 3 0^{\circ} 4 5^{\circ} 6 0^{\circ} 9 0^{\circ}

= \frac{π}{6}

= - \frac{π}{6}

- \frac{5 π}{6} + 2 πn < x < - \frac{π}{6} + 2 πn

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