Is 1/(sin(θ))-1/(tan(θ))=tan(θ/2) ?

The answer to whether 1/(sin(θ))-1/(tan(θ))=tan(θ/2) is True

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Popular >

prove 1/(sin(θ))-1/(tan(θ))=tan(θ/2)

Solution

prove

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

Solution

True

Solution steps

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

Let:

u = \frac{θ}{2}

\frac{1}{sin ( 2 u )} - \frac{1}{tan ( 2 u )} = tan (u)

Prove

\frac{1}{sin ( 2 u )} - \frac{1}{tan ( 2 u )} = tan (u) :

True

\frac{1}{sin ( 2 u )} - \frac{1}{tan ( 2 u )} = tan (u)

Manipulating left side

\frac{1}{sin ( 2 u )} - \frac{1}{tan ( 2 u )}

Express with sin, cos

\frac{1}{sin ( 2 u )} - \frac{1}{tan ( 2 u )}

Use the basic trigonometric identity:

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

= \frac{1}{sin ( 2 u )} - \frac{1}{\frac{s i n ( 2 u )}{c o s ( 2 u )}}

Simplify

\frac{1}{sin ( 2 u )} - \frac{1}{\frac{s i n ( 2 u )}{c o s ( 2 u )}} : \frac{1 - cos ( 2 u )}{sin ( 2 u )}

\frac{1}{sin ( 2 u )} - \frac{1}{\frac{s i n ( 2 u )}{c o s ( 2 u )}}

Apply the fraction rule:

\frac{1}{\frac{b}{c}} = \frac{c}{b}

= \frac{1}{sin ( 2 u )} - \frac{cos ( 2 u )}{sin ( 2 u )}

Apply rule

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

= \frac{1 - cos ( 2 u )}{sin ( 2 u )}

= \frac{1 - cos ( 2 u )}{sin ( 2 u )}

= \frac{1 - cos ( 2 u )}{sin ( 2 u )}

Rewrite using trig identities

\frac{1 - cos ( 2 u )}{sin ( 2 u )}

Use the Double Angle identity:

sin (2 x) = 2 sin (x) cos (x)

= \frac{1 - cos ( 2 u )}{2 sin ( u ) cos ( u )}

Use the Double Angle identity:

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

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

Simplify

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

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

Expand

1 - (1 - 2 sin^{2} (u)) : 2 sin^{2} (u)

1 - (1 - 2 sin^{2} (u))

- (1 - 2 sin^{2} (u)) : - 1 + 2 sin^{2} (u)

- (1 - 2 sin^{2} (u))

Distribute parentheses

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

Apply minus-plus rules

- (- a) = a, - (a) = - a

= - 1 + 2 sin^{2} (u)

= 1 - 1 + 2 sin^{2} (u)

1 - 1 = 0

= 2 sin^{2} (u)

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

Divide the numbers:

\frac{2}{2} = 1

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

Cancel the common factor:

sin (u)

= \frac{sin ( u )}{cos ( u )}

= \frac{sin ( u )}{cos ( u )}

= \frac{sin ( u )}{cos ( u )}

Use the basic trigonometric identity:

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

= tan (u)

We showed that the two sides could take the same form

\Rightarrow True

Therefore

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

We showed that the two sides could take the same form

\Rightarrow True

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Frequently Asked Questions (FAQ)

Is 1/(sin(θ))-1/(tan(θ))=tan(θ/2) ?
The answer to whether 1/(sin(θ))-1/(tan(θ))=tan(θ/2) is True