9. Simplify the following expression:

[tex]\[ \frac{\csc^2 \theta}{\cot \theta} = \csc \theta \sec \theta \][/tex]



Answer :

Sure! Let's solve the given trigonometric equation step-by-step:

Given: [tex]\(\frac{\csc ^2 \theta}{\cot \theta} = \csc \theta \sec \theta\)[/tex]

To prove this identity is true, we need to recall and use certain trigonometric identities:
1. [tex]\(\csc \theta = \frac{1}{\sin \theta}\)[/tex]
2. [tex]\(\sec \theta = \frac{1}{\cos \theta}\)[/tex]
3. [tex]\(\cot \theta = \frac{\cos \theta}{\sin \theta}\)[/tex]
4. [tex]\(\csc^2 \theta = \left(\frac{1}{\sin \theta}\right)^2 = \frac{1}{\sin^2 \theta}\)[/tex]

We will substitute these identities into the given equation.

Left-hand side (LHS):

[tex]\[ \frac{\csc ^2 \theta}{\cot \theta} = \frac{\frac{1}{\sin^2 \theta}}{\frac{\cos \theta}{\sin \theta}} \][/tex]

To simplify this, divide the numerator by the denominator:

[tex]\[ \frac{\frac{1}{\sin^2 \theta}}{\frac{\cos \theta}{\sin \theta}} = \frac{1}{\sin^2 \theta} \times \frac{\sin \theta}{\cos \theta} = \frac{1 \times \sin \theta}{\sin^2 \theta \times \cos \theta} = \frac{\sin \theta}{\sin^2 \theta \cos \theta} = \frac{1}{\sin \theta \cos \theta} \][/tex]

Right-hand side (RHS):

[tex]\[ \csc \theta \sec \theta = \left(\frac{1}{\sin \theta}\right) \left(\frac{1}{\cos \theta}\right) = \frac{1}{\sin \theta \cos \theta} \][/tex]

Comparison:

We see that the simplified LHS is:

[tex]\[ \frac{1}{\sin \theta \cos \theta} \][/tex]

And the RHS is also:

[tex]\[ \frac{1}{\sin \theta \cos \theta} \][/tex]

Since the LHS equals the RHS, the identity holds true.

Thus, the trigonometric identity [tex]\(\frac{\csc ^2 \theta}{\cot \theta} = \csc \theta \sec \theta\)[/tex] is indeed correct.