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Popular >

1-cos^2(y)>0

Solution

1 - cos^{2} (y) > 0

Solution

2 πn < y < π + 2 πn or π + 2 πn < y < 2 π + 2 πn

Interval Notation

(2 πn, π + 2 πn) \cup (π + 2 πn, 2 π + 2 πn)

Decimal Notation

2 πn < y < 3.14159 \dots + 2 πn or 3.14159 \dots + 2 πn < y < 6.28318 \dots + 2 πn

Solution steps

1 - cos^{2} (y) > 0

Move

1

to the right side

1 - cos^{2} (y) > 0

Subtract

1

from both sides

1 - cos^{2} (y) - 1 > 0 - 1

Simplify

- cos^{2} (y) > - 1

- cos^{2} (y) > - 1

Multiply both sides by

- 1

- cos^{2} (y) > - 1

Multiply both sides by -1 (reverse the inequality)

(- cos^{2} (y)) (- 1) < (- 1) (- 1)

Simplify

cos^{2} (y) < 1

cos^{2} (y) < 1

For

u^{n} < a

, if

n

is even then

- 1 < cos (y) < 1

a < u < b

then

a < u and u < b

- 1 < cos (y) and cos (y) < 1

- 1 < cos (y) : - π + 2 πn < y < π + 2 πn

- 1 < cos (y)

Switch sides

cos (y) > - 1

For

cos (x) > a

, if

- 1 \leq a < 1

then

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

- arccos (- 1) + 2 πn < y < arccos (- 1) + 2 πn

Simplify

- arccos (- 1) : - π

- arccos (- 1)

Use the following trivial identity:

arccos (- 1) = π

x - 1 - \frac{3}{2} - \frac{2}{2} - \frac{1}{2} 0 \frac{1}{2} \frac{2}{2} \frac{3}{2} 1 arccos (x) π \frac{5 π}{6} \frac{3 π}{4} \frac{2 π}{3} \frac{π}{2} \frac{π}{3} \frac{π}{4} \frac{π}{6} 0 arccos (x) 18 0^{\circ} 15 0^{\circ} 13 5^{\circ} 12 0^{\circ} 9 0^{\circ} 6 0^{\circ} 4 5^{\circ} 3 0^{\circ} 0^{\circ}

= - π

Simplify

arccos (- 1) : π

arccos (- 1)

Use the following trivial identity:

arccos (- 1) = π

x - 1 - \frac{3}{2} - \frac{2}{2} - \frac{1}{2} 0 \frac{1}{2} \frac{2}{2} \frac{3}{2} 1 arccos (x) π \frac{5 π}{6} \frac{3 π}{4} \frac{2 π}{3} \frac{π}{2} \frac{π}{3} \frac{π}{4} \frac{π}{6} 0 arccos (x) 18 0^{\circ} 15 0^{\circ} 13 5^{\circ} 12 0^{\circ} 9 0^{\circ} 6 0^{\circ} 4 5^{\circ} 3 0^{\circ} 0^{\circ}

= π

- π + 2 πn < y < π + 2 πn

cos (y) < 1 : 2 πn < y < 2 π + 2 πn

cos (y) < 1

For

cos (x) < a

, if

- 1 < a \leq 1

then

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

arccos (1) + 2 πn < y < 2 π - arccos (1) + 2 πn

Simplify

arccos (1) : 0

arccos (1)

Use the following trivial identity:

arccos (1) = 0

x - 1 - \frac{3}{2} - \frac{2}{2} - \frac{1}{2} 0 \frac{1}{2} \frac{2}{2} \frac{3}{2} 1 arccos (x) π \frac{5 π}{6} \frac{3 π}{4} \frac{2 π}{3} \frac{π}{2} \frac{π}{3} \frac{π}{4} \frac{π}{6} 0 arccos (x) 18 0^{\circ} 15 0^{\circ} 13 5^{\circ} 12 0^{\circ} 9 0^{\circ} 6 0^{\circ} 4 5^{\circ} 3 0^{\circ} 0^{\circ}

= 0

Simplify

2 π - arccos (1) : 2 π

2 π - arccos (1)

Use the following trivial identity:

arccos (1) = 0

x - 1 - \frac{3}{2} - \frac{2}{2} - \frac{1}{2} 0 \frac{1}{2} \frac{2}{2} \frac{3}{2} 1 arccos (x) π \frac{5 π}{6} \frac{3 π}{4} \frac{2 π}{3} \frac{π}{2} \frac{π}{3} \frac{π}{4} \frac{π}{6} 0 arccos (x) 18 0^{\circ} 15 0^{\circ} 13 5^{\circ} 12 0^{\circ} 9 0^{\circ} 6 0^{\circ} 4 5^{\circ} 3 0^{\circ} 0^{\circ}

= 2 π - 0

2 π - 0 = 2 π

= 2 π

0 + 2 πn < y < 2 π + 2 πn

Simplify

2 πn < y < 2 π + 2 πn

Combine the intervals

- π + 2 πn < y < π + 2 πn and 2 πn < y < 2 π + 2 πn

Merge Overlapping Intervals

2 πn < y < π + 2 πn or π + 2 πn < y < 2 π + 2 πn

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