Simplify and prove the following trigonometric identity:

[tex]\[ (\operatorname{cosec} \theta - \cot \theta)^2 = \frac{1 - \cos \theta}{1 + \cos \theta} \][/tex]



Answer :

Alright, let's solve the equation step by step to verify the given trigonometric identity:

[tex]\[ (\csc \theta - \cot \theta)^2 = \frac{1 - \cos \theta}{1 + \cos \theta} \][/tex]

First, let's express the left-hand side of the equation using basic trigonometric identities. Recall that cosecant and cotangent are defined as:
[tex]\[ \csc \theta = \frac{1}{\sin \theta} \quad \text{and} \quad \cot \theta = \frac{\cos \theta}{\sin \theta} \][/tex]

Substitute these into the left-hand side:
[tex]\[ (\csc \theta - \cot \theta)^2 = \left(\frac{1}{\sin \theta} - \frac{\cos \theta}{\sin \theta}\right)^2 \][/tex]

Combine the terms inside the parentheses:
[tex]\[ = \left(\frac{1 - \cos \theta}{\sin \theta}\right)^2 \][/tex]

Simplify the expression:
[tex]\[ = \frac{(1 - \cos \theta)^2}{\sin^2 \theta} \][/tex]

Now, consider the right-hand side of the equation:
[tex]\[ \frac{1 - \cos \theta}{1 + \cos \theta} \][/tex]

We need to determine if the simplified left-hand side equals the right-hand side. Recall the Pythagorean identity:
[tex]\[ \sin^2 \theta = 1 - \cos^2 \theta \][/tex]

Hence,
[tex]\[ \frac{(1 - \cos \theta)^2}{\sin^2 \theta} = \frac{(1 - \cos \theta)^2}{1 - \cos^2 \theta} \][/tex]

Observe that [tex]\(1 - \cos^2 \theta\)[/tex] can be written as:
[tex]\[ 1 - \cos^2 \theta = (1 - \cos \theta)(1 + \cos \theta) \][/tex]

So,
[tex]\[ \frac{(1 - \cos \theta)^2}{1 - \cos^2 \theta} = \frac{(1 - \cos \theta)^2}{(1 - \cos \theta)(1 + \cos \theta)} \][/tex]

Cancel out [tex]\(1 - \cos \theta\)[/tex] in the numerator and denominator:
[tex]\[ = \frac{1 - \cos \theta}{1 + \cos \theta} \][/tex]

Thus, we have shown that:

[tex]\[ (\csc \theta - \cot \theta)^2 = \frac{1 - \cos \theta}{1 + \cos \theta} \][/tex]

So, the identity is verified to be true.