What is the general solution for cot^2(x)=-2cot(x)-1 ?

The general solution for cot^2(x)=-2cot(x)-1 is x=(3pi)/4+pin

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

Solution

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

Solution

x = \frac{3 π}{4} + πn

Degrees

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

Solution steps

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

Solve by substitution

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

Let:

cot (x) = u

u^{2} = - 2 u - 1

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

u^{2} = - 2 u - 1

Move

1

to the left side

u^{2} = - 2 u - 1

Add

1

to both sides

u^{2} + 1 = - 2 u - 1 + 1

Simplify

u^{2} + 1 = - 2 u

u^{2} + 1 = - 2 u

Move

2 u

to the left side

u^{2} + 1 = - 2 u

Add

2 u

to both sides

u^{2} + 1 + 2 u = - 2 u + 2 u

Simplify

u^{2} + 1 + 2 u = 0

u^{2} + 1 + 2 u = 0

Write in the standard form

a x^{2} + b x + c = 0

u^{2} + 2 u + 1 = 0

Solve with the quadratic formula

u^{2} + 2 u + 1 = 0

Quadratic Equation Formula:

For

a = 1, b = 2, c = 1

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

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

2^{2} - 4 \cdot 1 \cdot 1 = 0

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

Multiply the numbers:

4 \cdot 1 \cdot 1 = 4

= 2^{2} - 4

2^{2} = 4

= 4 - 4

Subtract the numbers:

4 - 4 = 0

= 0

u_{1, 2} = \frac{- 2 \pm 0}{2 \cdot 1}

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

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

\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

u = - 1

The solution to the quadratic equation is:

u = - 1

Substitute back

u = cot (x)

cot (x) = - 1

cot (x) = - 1

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 = \frac{3 π}{4} + πn

Popular Examples

cos((pit)/2)=0

cos (\frac{π t}{2}) = 0

sin(θ)=-3/7

sin (θ) = - \frac{3}{7}

tan(θ)=(sqrt(3))/(-1)

tan (θ) = \frac{3}{- 1}

cos(x)= 8/10

cos (x) = \frac{8}{10}

2sin^2(x)+3=0

2 sin^{2} (x) + 3 = 0

Frequently Asked Questions (FAQ)

What is the general solution for cot^2(x)=-2cot(x)-1 ?
The general solution for cot^2(x)=-2cot(x)-1 is x=(3pi)/4+pin