What is the general solution for tan(2θ)=(2tan(θ))/(1-tan(θ)) ?

The general solution for tan(2θ)=(2tan(θ))/(1-tan(θ)) is θ=pin

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tan(2θ)=(2tan(θ))/(1-tan(θ))

Solution

tan (2 θ) = \frac{2 tan ( θ )}{1 - tan ( θ )}

Solution

θ = πn

Degrees

θ = 0^{\circ} + 18 0^{\circ} n

Solution steps

tan (2 θ) = \frac{2 tan ( θ )}{1 - tan ( θ )}

Subtract

\frac{2 tan ( θ )}{1 - tan ( θ )}

from both sides

tan (2 θ) - \frac{2 tan ( θ )}{1 - tan ( θ )} = 0

Simplify

tan (2 θ) - \frac{2 tan ( θ )}{1 - tan ( θ )} : \frac{tan ( 2 θ ) ( 1 - tan ( θ ) ) - 2 tan ( θ )}{1 - tan ( θ )}

tan (2 θ) - \frac{2 tan ( θ )}{1 - tan ( θ )}

Convert element to fraction:

tan (2 θ) = \frac{tan ( 2 θ ) ( 1 - tan ( θ ) )}{1 - tan ( θ )}

= \frac{tan ( 2 θ ) ( 1 - tan ( θ ) )}{1 - tan ( θ )} - \frac{2 tan ( θ )}{1 - tan ( θ )}

Since the denominators are equal, combine the fractions:

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

= \frac{tan ( 2 θ ) ( 1 - tan ( θ ) ) - 2 tan ( θ )}{1 - tan ( θ )}

\frac{tan ( 2 θ ) ( 1 - tan ( θ ) ) - 2 tan ( θ )}{1 - tan ( θ )} = 0

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

tan (2 θ) (1 - tan (θ)) - 2 tan (θ) = 0

Rewrite using trig identities

(1 - tan (θ)) tan (2 θ) - 2 tan (θ)

Use the Double Angle identity:

tan (2 x) = \frac{2 tan ( x )}{1 - tan ^{2} ( x )}

= - 2 tan (θ) + \frac{2 tan ( θ )}{1 - tan ^{2} ( θ )} (1 - tan (θ))

Simplify

- 2 tan (θ) + \frac{2 tan ( θ )}{1 - tan ^{2} ( θ )} (1 - tan (θ)) : - \frac{2 tan ^{2} ( θ )}{tan ( θ ) + 1}

- 2 tan (θ) + \frac{2 tan ( θ )}{1 - tan ^{2} ( θ )} (1 - tan (θ))

\frac{2 tan ( θ )}{1 - tan ^{2} ( θ )} (1 - tan (θ)) = \frac{2 tan ( θ )}{tan ( θ ) + 1}

\frac{2 tan ( θ )}{1 - tan ^{2} ( θ )} (1 - tan (θ))

Multiply fractions:

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

= \frac{2 tan ( θ ) ( 1 - tan ( θ ) )}{1 - tan ^{2} ( θ )}

Factor

1 - tan (θ) : - (tan (θ) - 1)

1 - tan (θ)

Factor out common term

- 1

= - (tan (θ) - 1)

= - \frac{2 tan ( θ ) ( tan ( θ ) - 1 )}{1 - tan ^{2} ( θ )}

Factor

1 - tan^{2} (θ) : - (tan (θ) + 1) (tan (θ) - 1)

1 - tan^{2} (θ)

Factor out common term

- 1

= - (tan^{2} (θ) - 1)

Factor

tan^{2} (θ) - 1 : (tan (θ) + 1) (tan (θ) - 1)

tan^{2} (θ) - 1

Rewrite

1

1^{2}

= tan^{2} (θ) - 1^{2}

Apply Difference of Two Squares Formula:

x^{2} - y^{2} = (x + y) (x - y)

tan^{2} (θ) - 1^{2} = (tan (θ) + 1) (tan (θ) - 1)

= (tan (θ) + 1) (tan (θ) - 1)

= - (tan (θ) + 1) (tan (θ) - 1)

= \frac{2 tan ( θ ) ( tan ( θ ) - 1 )}{( tan ( θ ) + 1 ) ( tan ( θ ) - 1 )}

Cancel the common factor:

tan (θ) - 1

= \frac{2 tan ( θ )}{tan ( θ ) + 1}

= - 2 tan (θ) + \frac{2 tan ( θ )}{tan ( θ ) + 1}

Convert element to fraction:

2 tan (θ) = \frac{2 tan ( θ ) ( tan ( θ ) + 1 )}{tan ( θ ) + 1}

= \frac{2 tan ( θ )}{tan ( θ ) + 1} - \frac{2 tan ( θ ) ( tan ( θ ) + 1 )}{tan ( θ ) + 1}

Since the denominators are equal, combine the fractions:

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

= \frac{2 tan ( θ ) - 2 tan ( θ ) ( tan ( θ ) + 1 )}{tan ( θ ) + 1}

Expand

2 tan (θ) - 2 tan (θ) (tan (θ) + 1) : - 2 tan^{2} (θ)

2 tan (θ) - 2 tan (θ) (tan (θ) + 1)

Expand

- 2 tan (θ) (tan (θ) + 1) : - 2 tan^{2} (θ) - 2 tan (θ)

- 2 tan (θ) (tan (θ) + 1)

Apply the distributive law:

a (b + c) = ab + a c

a = - 2 tan (θ), b = tan (θ), c = 1

= - 2 tan (θ) tan (θ) + (- 2 tan (θ)) \cdot 1

Apply minus-plus rules

+ (- a) = - a

= - 2 tan (θ) tan (θ) - 2 \cdot 1 \cdot tan (θ)

Simplify

- 2 tan (θ) tan (θ) - 2 \cdot 1 \cdot tan (θ) : - 2 tan^{2} (θ) - 2 tan (θ)

- 2 tan (θ) tan (θ) - 2 \cdot 1 \cdot tan (θ)

2 tan (θ) tan (θ) = 2 tan^{2} (θ)

2 tan (θ) tan (θ)

Apply exponent rule:

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

tan (θ) tan (θ) = tan^{1 + 1} (θ)

= 2 tan^{1 + 1} (θ)

Add the numbers:

1 + 1 = 2

= 2 tan^{2} (θ)

2 \cdot 1 \cdot tan (θ) = 2 tan (θ)

2 \cdot 1 \cdot tan (θ)

Multiply the numbers:

2 \cdot 1 = 2

= 2 tan (θ)

= - 2 tan^{2} (θ) - 2 tan (θ)

= - 2 tan^{2} (θ) - 2 tan (θ)

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

Add similar elements:

2 tan (θ) - 2 tan (θ) = 0

= - 2 tan^{2} (θ)

= \frac{- 2 tan ^{2} ( θ )}{tan ( θ ) + 1}

Apply the fraction rule:

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

= - \frac{2 tan ^{2} ( θ )}{tan ( θ ) + 1}

= - \frac{2 tan ^{2} ( θ )}{tan ( θ ) + 1}

- \frac{2 tan ^{2} ( θ )}{1 + tan ( θ )} = 0

Solve by substitution

- \frac{2 tan ^{2} ( θ )}{1 + tan ( θ )} = 0

Let:

tan (θ) = u

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

- \frac{2 u ^{2}}{1 + u} = 0 : u = 0

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

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

2 u^{2} = 0

Solve

2 u^{2} = 0 : u = 0

2 u^{2} = 0

Divide both sides by

2

2 u^{2} = 0

Divide both sides by

2

2 u^{2} = 0

Divide both sides by

2

\frac{2 u ^{2}}{2} = \frac{0}{2}

Simplify

u^{2} = 0

u^{2} = 0

Apply rule

x^{n} = 0 \Rightarrow x = 0

u = 0

u = 0

Verify Solutions

Find undefined (singularity) points:

u = - 1

Take the denominator(s) of

- \frac{2 u ^{2}}{1 + u}

and compare to zero

Solve

1 + u = 0 : u = - 1

1 + u = 0

Move

1

to the right side

1 + u = 0

Subtract

1

from both sides

1 + u - 1 = 0 - 1

Simplify

u = - 1

u = - 1

The following points are undefined

u = - 1

Combine undefined points with solutions:

u = 0

Substitute back

u = tan (θ)

tan (θ) = 0

tan (θ) = 0

tan (θ) = 0 : θ = πn

tan (θ) = 0

General solutions for

tan (θ) = 0

tan (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} tan (x) 0 \frac{3}{3} 13 \pm \infty - 3 - 1 - \frac{3}{3}

θ = 0 + πn

θ = 0 + πn

Solve

θ = 0 + πn : θ = πn

θ = 0 + πn

0 + πn = πn

θ = πn

θ = πn

Combine all the solutions

θ = πn

Popular Examples

sec(θ)=15,tan(2θ)+125(cos(2θ)-1)

sec (θ) = 15, tan (2 θ) + 125 (cos (2 θ) - 1)

sqrt(2)cos(θ)+1=0

2 cos (θ) + 1 = 0

1/(1-sin(x))=2sec^2(x)+tan(x)sec(x)

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

4sqrt(2)tan(x)-sqrt(2)=3sqrt(2)tan(x)

42 tan (x) - 2 = 32 tan (x)

7sin(2x)+12cos(x)=0

7 sin (2 x) + 12 cos (x) = 0

Frequently Asked Questions (FAQ)

What is the general solution for tan(2θ)=(2tan(θ))/(1-tan(θ)) ?
The general solution for tan(2θ)=(2tan(θ))/(1-tan(θ)) is θ=pin