English

Español

Português

Français

Deutsch

Italiano

Русский

中文(简体)

한국어

日本語

Tiếng Việt

עברית

العربية

Popular >

csc^2(θ)-2csc(θ)-8=0

Solution

csc^{2} (θ) - 2 csc (θ) - 8 = 0

Solution

θ = 0.25268 \dots + 2 πn, θ = π - 0.25268 \dots + 2 πn, θ = \frac{7 π}{6} + 2 πn, θ = \frac{11 π}{6} + 2 πn

Degrees

θ = 14.47751 \dots^{\circ} + 36 0^{\circ} n, θ = 165.52248 \dots^{\circ} + 36 0^{\circ} n, θ = 21 0^{\circ} + 36 0^{\circ} n, θ = 33 0^{\circ} + 36 0^{\circ} n

Solution steps

csc^{2} (θ) - 2 csc (θ) - 8 = 0

Solve by substitution

csc^{2} (θ) - 2 csc (θ) - 8 = 0

Let:

csc (θ) = u

u^{2} - 2 u - 8 = 0

u^{2} - 2 u - 8 = 0 : u = 4, u = - 2

u^{2} - 2 u - 8 = 0

Solve with the quadratic formula

u^{2} - 2 u - 8 = 0

Quadratic Equation Formula:

For

a = 1, b = - 2, c = - 8

u_{1, 2} = \frac{- ( - 2 ) \pm ( - 2 ) ^{2} - 4 \cdot 1 \cdot ( - 8 )}{2 \cdot 1}

u_{1, 2} = \frac{- ( - 2 ) \pm ( - 2 ) ^{2} - 4 \cdot 1 \cdot ( - 8 )}{2 \cdot 1}

(- 2)^{2} - 4 \cdot 1 \cdot (- 8) = 6

(- 2)^{2} - 4 \cdot 1 \cdot (- 8)

Apply rule

- (- a) = a

= (- 2)^{2} + 4 \cdot 1 \cdot 8

Apply exponent rule:

(- a)^{n} = a^{n},

n

is even

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

= 2^{2} + 4 \cdot 1 \cdot 8

Multiply the numbers:

4 \cdot 1 \cdot 8 = 32

= 2^{2} + 32

2^{2} = 4

= 4 + 32

Add the numbers:

4 + 32 = 36

= 36

Factor the number:

36 = 6^{2}

= 6^{2}

Apply radical rule:

6^{2} = 6

= 6

u_{1, 2} = \frac{- ( - 2 ) \pm 6}{2 \cdot 1}

Separate the solutions

u_{1} = \frac{- ( - 2 ) + 6}{2 \cdot 1}, u_{2} = \frac{- ( - 2 ) - 6}{2 \cdot 1}

u = \frac{- ( - 2 ) + 6}{2 \cdot 1} : 4

\frac{- ( - 2 ) + 6}{2 \cdot 1}

Apply rule

- (- a) = a

= \frac{2 + 6}{2 \cdot 1}

Add the numbers:

2 + 6 = 8

= \frac{8}{2 \cdot 1}

Multiply the numbers:

2 \cdot 1 = 2

= \frac{8}{2}

Divide the numbers:

\frac{8}{2} = 4

= 4

u = \frac{- ( - 2 ) - 6}{2 \cdot 1} : - 2

\frac{- ( - 2 ) - 6}{2 \cdot 1}

Apply rule

- (- a) = a

= \frac{2 - 6}{2 \cdot 1}

Subtract the numbers:

2 - 6 = - 4

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

Multiply the numbers:

2 \cdot 1 = 2

= \frac{- 4}{2}

Apply the fraction rule:

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

= - \frac{4}{2}

Divide the numbers:

\frac{4}{2} = 2

= - 2

The solutions to the quadratic equation are:

u = 4, u = - 2

Substitute back

u = csc (θ)

csc (θ) = 4, csc (θ) = - 2

csc (θ) = 4, csc (θ) = - 2

csc (θ) = 4 : θ = arccsc (4) + 2 πn, θ = π - arccsc (4) + 2 πn

csc (θ) = 4

Apply trig inverse properties

csc (θ) = 4

General solutions for

csc (θ) = 4

csc (x) = a \Rightarrow x = arccsc (a) + 2 πn, x = π - arccsc (a) + 2 πn

θ = arccsc (4) + 2 πn, θ = π - arccsc (4) + 2 πn

θ = arccsc (4) + 2 πn, θ = π - arccsc (4) + 2 πn

csc (θ) = - 2 : θ = \frac{7 π}{6} + 2 πn, θ = \frac{11 π}{6} + 2 πn

csc (θ) = - 2

General solutions for

csc (θ) = - 2

csc (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} csc (x) Undefiend 22 \frac{2 3}{3} 1 \frac{2 3}{3} 22 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} csc (x) Undefiend - 2 - 2 - \frac{2 3}{3} - 1 - \frac{2 3}{3} - 2 - 2

θ = \frac{7 π}{6} + 2 πn, θ = \frac{11 π}{6} + 2 πn

θ = \frac{7 π}{6} + 2 πn, θ = \frac{11 π}{6} + 2 πn

Combine all the solutions

θ = arccsc (4) + 2 πn, θ = π - arccsc (4) + 2 πn, θ = \frac{7 π}{6} + 2 πn, θ = \frac{11 π}{6} + 2 πn

Show solutions in decimal form

θ = 0.25268 \dots + 2 πn, θ = π - 0.25268 \dots + 2 πn, θ = \frac{7 π}{6} + 2 πn, θ = \frac{11 π}{6} + 2 πn

Popular Examples

(tan(θ)+1)(cos(θ)+1)=0

(tan (θ) + 1) (cos (θ) + 1) = 0

sec(θ)= 5/3

sec (θ) = \frac{5}{3}

1-cos(x)=sqrt(3)sin(x)

1 - cos (x) = 3 sin (x)

sin(θ)= 7/25

sin (θ) = \frac{7}{25}

tan(x)= 4/5

tan (x) = \frac{4}{5}