What is the general solution for cot^3(x)+cot(x)=0 ?

The general solution for cot^3(x)+cot(x)=0 is x= pi/2+pin

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cot^3(x)+cot(x)=0

Solution

cot^{3} (x) + cot (x) = 0

Solution

x = \frac{π}{2} + πn

Degrees

x = 9 0^{\circ} + 18 0^{\circ} n

Solution steps

cot^{3} (x) + cot (x) = 0

Solve by substitution

cot^{3} (x) + cot (x) = 0

Let:

cot (x) = u

u^{3} + u = 0

u^{3} + u = 0 : u = 0, u = i, u = - i

u^{3} + u = 0

Factor

u^{3} + u : u (u^{2} + 1)

u^{3} + u

Apply exponent rule:

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

u^{3} = u^{2} u

= u^{2} u + u

Factor out common term

u

= u (u^{2} + 1)

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

Using the Zero Factor Principle:

ab = 0

then

a = 0

b = 0

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

Solve

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

u^{2} + 1 = 0

Move

1

to the right side

u^{2} + 1 = 0

Subtract

1

from both sides

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

Simplify

u^{2} = - 1

u^{2} = - 1

For

x^{2} = f (a)

the solutions are

x = f (a), - f (a)

u = - 1, u = - - 1

Simplify

- 1 : i

- 1

Apply imaginary number rule:

- 1 = i

= i

Simplify

- - 1 : - i

- - 1

Apply imaginary number rule:

- 1 = i

= - i

u = i, u = - i

The solutions are

u = 0, u = i, u = - i

Substitute back

u = cot (x)

cot (x) = 0, cot (x) = i, cot (x) = - i

cot (x) = 0, cot (x) = i, cot (x) = - i

cot (x) = 0 : x = \frac{π}{2} + πn

cot (x) = 0

General solutions for

cot (x) = 0

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{π}{2} + πn

x = \frac{π}{2} + πn

cot (x) = i :

No Solution

cot (x) = i

No Solution

cot (x) = - i :

No Solution

cot (x) = - i

No Solution

Combine all the solutions

x = \frac{π}{2} + πn

Popular Examples

21+18cos(x)=16(1-cos^2(x))

21 + 18 cos (x) = 16 (1 - cos^{2} (x))

sin(2a+10)=cos(3a-20)

sin (2 a + 10) = cos (3 a - 20)

b= 3/((cot(x)))

b = \frac{3}{( cot ( x ) )}

4sin^2(x)+cos(x)+1=0

4 sin^{2} (x) + cos (x) + 1 = 0

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

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

Frequently Asked Questions (FAQ)

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