What is the general solution for cos(x)*sec(x)*cot^2(x)=csc^2(x) ?

The general solution for cos(x)*sec(x)*cot^2(x)=csc^2(x) is No Solution for x\in\mathbb{R}

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cos(x)sec(x)cot^2(x)=csc^2(x)

Solution

cos (x) \cdot sec (x) \cdot cot^{2} (x) = csc^{2} (x)

Solution

No Solution for x \in R

Solution steps

cos (x) sec (x) cot^{2} (x) = csc^{2} (x)

Subtract

csc^{2} (x)

from both sides

cot^{2} (x) cos (x) sec (x) - csc^{2} (x) = 0

Express with sin, cos

- csc^{2} (x) + cos (x) cot^{2} (x) sec (x)

Use the basic trigonometric identity:

csc (x) = \frac{1}{sin ( x )}

= - (\frac{1}{sin ( x )})^{2} + cos (x) cot^{2} (x) sec (x)

Use the basic trigonometric identity:

cot (x) = \frac{cos ( x )}{sin ( x )}

= - (\frac{1}{sin ( x )})^{2} + cos (x) (\frac{cos ( x )}{sin ( x )})^{2} sec (x)

Use the basic trigonometric identity:

sec (x) = \frac{1}{cos ( x )}

= - (\frac{1}{sin ( x )})^{2} + cos (x) (\frac{cos ( x )}{sin ( x )})^{2} \frac{1}{cos ( x )}

Simplify

- (\frac{1}{sin ( x )})^{2} + cos (x) (\frac{cos ( x )}{sin ( x )})^{2} \frac{1}{cos ( x )} : \frac{- 1 + cos ^{2} ( x )}{sin ^{2} ( x )}

- (\frac{1}{sin ( x )})^{2} + cos (x) (\frac{cos ( x )}{sin ( x )})^{2} \frac{1}{cos ( x )}

(\frac{1}{sin ( x )})^{2} = \frac{1}{sin ^{2} ( x )}

(\frac{1}{sin ( x )})^{2}

Apply exponent rule:

(\frac{a}{b})^{c} = \frac{a ^{c}}{b ^{c}}

= \frac{1 ^{2}}{sin ^{2} ( x )}

Apply rule

1^{a} = 1

1^{2} = 1

= \frac{1}{sin ^{2} ( x )}

cos (x) (\frac{cos ( x )}{sin ( x )})^{2} \frac{1}{cos ( x )} = \frac{cos ^{2} ( x )}{sin ^{2} ( x )}

cos (x) (\frac{cos ( x )}{sin ( x )})^{2} \frac{1}{cos ( x )}

Multiply fractions:

a \cdot \frac{b}{c} = \frac{a \cdot b}{c}

= \frac{1 \cdot cos ( x ) ( \frac{c o s ( x )}{s i n ( x )} ) ^{2}}{cos ( x )}

Cancel the common factor:

cos (x)

= 1 \cdot (\frac{cos ( x )}{sin ( x )})^{2}

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

(\frac{cos ( x )}{sin ( x )})^{2}

Apply exponent rule:

(\frac{a}{b})^{c} = \frac{a ^{c}}{b ^{c}}

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

= 1 \cdot \frac{cos ^{2} ( x )}{sin ^{2} ( x )}

Multiply:

1 \cdot \frac{cos ^{2} ( x )}{sin ^{2} ( x )} = \frac{cos ^{2} ( x )}{sin ^{2} ( x )}

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

= - \frac{1}{sin ^{2} ( x )} + \frac{cos ^{2} ( x )}{sin ^{2} ( x )}

Apply rule

\frac{a}{c} \pm \frac{b}{c} = \frac{a \pm b}{c}

= \frac{- 1 + cos ^{2} ( x )}{sin ^{2} ( x )}

= \frac{- 1 + cos ^{2} ( x )}{sin ^{2} ( x )}

\frac{- 1 + cos ^{2} ( x )}{sin ^{2} ( x )} = 0

\frac{f ( x )}{g ( x )} = 0 \Rightarrow f (x) = 0

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

Solve by substitution

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

Let:

cos (x) = u

- 1 + u^{2} = 0

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

- 1 + u^{2} = 0

Move

1

to the right side

- 1 + u^{2} = 0

Add

1

to both sides

- 1 + u^{2} + 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

1 = 1

1

Apply rule

1 = 1

= 1

- 1 = - 1

- 1

Apply rule

1 = 1

= - 1

u = 1, u = - 1

Substitute back

u = cos (x)

cos (x) = 1, cos (x) = - 1

cos (x) = 1, cos (x) = - 1

cos (x) = 1 : x = 2 πn

cos (x) = 1

General solutions for

cos (x) = 1

cos (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} cos (x) 1 \frac{3}{2} \frac{2}{2} \frac{1}{2} 0 - \frac{1}{2} - \frac{2}{2} - \frac{3}{2} 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} cos (x) - 1 - \frac{3}{2} - \frac{2}{2} - \frac{1}{2} 0 \frac{1}{2} \frac{2}{2} \frac{3}{2}

x = 0 + 2 πn

x = 0 + 2 πn

Solve

x = 0 + 2 πn : x = 2 πn

x = 0 + 2 πn

0 + 2 πn = 2 πn

x = 2 πn

x = 2 πn

cos (x) = - 1 : x = π + 2 πn

cos (x) = - 1

General solutions for

cos (x) = - 1

cos (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} cos (x) 1 \frac{3}{2} \frac{2}{2} \frac{1}{2} 0 - \frac{1}{2} - \frac{2}{2} - \frac{3}{2} 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} cos (x) - 1 - \frac{3}{2} - \frac{2}{2} - \frac{1}{2} 0 \frac{1}{2} \frac{2}{2} \frac{3}{2}

x = π + 2 πn

x = π + 2 πn

Combine all the solutions

x = 2 πn, x = π + 2 πn

Since the equation is undefined for:

2 πn, π + 2 πn

No Solution for x \in R

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sin (θ) = \frac{7}{15}

Frequently Asked Questions (FAQ)

What is the general solution for cos(x)*sec(x)*cot^2(x)=csc^2(x) ?
The general solution for cos(x)*sec(x)*cot^2(x)=csc^2(x) is No Solution for x\in\mathbb{R}