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Simplify the following expression:

[tex]\sqrt{1-\sin ^2 A} \cdot \operatorname{cosec} A=\cot A[/tex]


Sagot :

Let's solve the given equation step by step:

[tex]\[ \sqrt{1 - \sin^2(A)} \cdot \csc(A) = \cot(A) \][/tex]

First, we need to use some fundamental trigonometric identities to simplify this expression.

1. Pythagorean Identity: We know that for any angle [tex]\(A\)[/tex],
[tex]\[ \sin^2(A) + \cos^2(A) = 1 \][/tex]
Therefore,
[tex]\[ \cos^2(A) = 1 - \sin^2(A) \][/tex]
Taking the square root of both sides, we get:
[tex]\[ \sqrt{1 - \sin^2(A)} = \cos(A) \][/tex]

2. Reciprocal Identities:
- The cosecant function is the reciprocal of the sine function:
[tex]\[ \csc(A) = \frac{1}{\sin(A)} \][/tex]
- The cotangent function is defined as the ratio of cosine to sine:
[tex]\[ \cot(A) = \frac{\cos(A)}{\sin(A)} \][/tex]

Now, substitute these identities back into the given equation:

The left side of the equation:
[tex]\[ \sqrt{1 - \sin^2(A)} \cdot \csc(A) \][/tex]
becomes:
[tex]\[ \cos(A) \cdot \frac{1}{\sin(A)} \][/tex]
which simplifies to:
[tex]\[ \frac{\cos(A)}{\sin(A)} \][/tex]

So, the equation now is:
[tex]\[ \frac{\cos(A)}{\sin(A)} = \cot(A) \][/tex]

Since [tex]\(\frac{\cos(A)}{\sin(A)}\)[/tex] is indeed the definition of [tex]\(\cot(A)\)[/tex], the given equation holds true. Thus, we have shown that:

[tex]\[ \sqrt{1 - \sin^2(A)} \cdot \csc(A) = \cot(A) \][/tex]

This confirms that the given equation is a true trigonometric identity.