What is the general solution for cot^2(x)-cot(x)-2=0 ?

The general solution for cot^2(x)-cot(x)-2=0 is x=0.46364…+pin,x=(3pi)/4+pin

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cot^2(x)-cot(x)-2=0

Solution

cot^{2} (x) - cot (x) - 2 = 0

Solution

x = 0.46364 \dots + πn, x = \frac{3 π}{4} + πn

Degrees

x = 26.56505 \dots^{\circ} + 18 0^{\circ} n, x = 13 5^{\circ} + 18 0^{\circ} n

Solution steps

cot^{2} (x) - cot (x) - 2 = 0

Solve by substitution

cot^{2} (x) - cot (x) - 2 = 0

Let:

cot (x) = u

u^{2} - u - 2 = 0

u^{2} - u - 2 = 0 : u = 2, u = - 1

u^{2} - u - 2 = 0

Solve with the quadratic formula

u^{2} - u - 2 = 0

Quadratic Equation Formula:

For

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

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

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

(- 1)^{2} - 4 \cdot 1 \cdot (- 2) = 3

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

Apply rule

- (- a) = a

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

(- 1)^{2} = 1

(- 1)^{2}

Apply exponent rule:

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

n

is even

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

= 1^{2}

Apply rule

1^{a} = 1

= 1

4 \cdot 1 \cdot 2 = 8

4 \cdot 1 \cdot 2

Multiply the numbers:

4 \cdot 1 \cdot 2 = 8

= 8

= 1 + 8

Add the numbers:

1 + 8 = 9

= 9

Factor the number:

9 = 3^{2}

= 3^{2}

Apply radical rule:

3^{2} = 3

= 3

u_{1, 2} = \frac{- ( - 1 ) \pm 3}{2 \cdot 1}

Separate the solutions

u_{1} = \frac{- ( - 1 ) + 3}{2 \cdot 1}, u_{2} = \frac{- ( - 1 ) - 3}{2 \cdot 1}

u = \frac{- ( - 1 ) + 3}{2 \cdot 1} : 2

\frac{- ( - 1 ) + 3}{2 \cdot 1}

Apply rule

- (- a) = a

= \frac{1 + 3}{2 \cdot 1}

Add the numbers:

1 + 3 = 4

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

Multiply the numbers:

2 \cdot 1 = 2

= \frac{4}{2}

Divide the numbers:

\frac{4}{2} = 2

= 2

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

\frac{- ( - 1 ) - 3}{2 \cdot 1}

Apply rule

- (- a) = a

= \frac{1 - 3}{2 \cdot 1}

Subtract the numbers:

1 - 3 = - 2

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

Multiply the numbers:

2 \cdot 1 = 2

= \frac{- 2}{2}

Apply the fraction rule:

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

= - \frac{2}{2}

Apply rule

\frac{a}{a} = 1

= - 1

The solutions to the quadratic equation are:

u = 2, u = - 1

Substitute back

u = cot (x)

cot (x) = 2, cot (x) = - 1

cot (x) = 2, cot (x) = - 1

cot (x) = 2 : x = arccot (2) + πn

cot (x) = 2

Apply trig inverse properties

cot (x) = 2

General solutions for

cot (x) = 2

cot (x) = a \Rightarrow x = arccot (a) + πn

x = arccot (2) + πn

x = arccot (2) + πn

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

cot (x) = - 1

General solutions for

cot (x) = - 1

cot (x)

periodicity table with

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} cot (x) \mp \infty 31 \frac{3}{3} 0 - \frac{3}{3} - 1 - 3

x = \frac{3 π}{4} + πn

x = \frac{3 π}{4} + πn

Combine all the solutions

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

Show solutions in decimal form

x = 0.46364 \dots + πn, x = \frac{3 π}{4} + πn

Popular Examples

cos^2(θ)=0.1831

cos^{2} (θ) = 0.1831

tan(a+5)=sqrt(2sin(30)+sec(245))

tan (a + 5^{\circ}) = 2 sin (3 0^{\circ}) + sec (24 5^{\circ})

cot(x)=tan(25)

cot (x) = tan (2 5^{\circ})

2sin(2θ)=cos(2θ+30)

2 sin (2 θ) = cos (2 θ + 3 0^{\circ})

cos^2(x)= 3/2

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

Frequently Asked Questions (FAQ)

What is the general solution for cot^2(x)-cot(x)-2=0 ?
The general solution for cot^2(x)-cot(x)-2=0 is x=0.46364…+pin,x=(3pi)/4+pin