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What is [tex]$\sin (\theta)$[/tex] if [tex]$\cos (\theta) = \frac{5}{13}$[/tex]? Express your answer as a reduced fraction.

[tex]\sin (\theta) =[/tex]

Sagot :

To find [tex]\(\sin(\theta)\)[/tex] given that [tex]\(\cos(\theta) = \frac{5}{13}\)[/tex], we can use the Pythagorean identity:

[tex]\[ \sin^2(\theta) + \cos^2(\theta) = 1 \][/tex]

First, let's square the given [tex]\(\cos(\theta)\)[/tex]:

[tex]\[ \cos^2(\theta) = \left(\frac{5}{13}\right)^2 = \frac{25}{169} \][/tex]

Then we use the Pythagorean identity to find [tex]\(\sin^2(\theta)\)[/tex]:

[tex]\[ \sin^2(\theta) = 1 - \cos^2(\theta) = 1 - \frac{25}{169} \][/tex]

Next, we need a common denominator to subtract the fractions:

[tex]\[ 1 = \frac{169}{169} \quad \text{so} \quad 1 - \frac{25}{169} = \frac{169}{169} - \frac{25}{169} = \frac{144}{169} \][/tex]

Now, we take the square root of [tex]\(\sin^2(\theta)\)[/tex] to find [tex]\(\sin(\theta)\)[/tex]:

[tex]\[ \sin(\theta) = \sqrt{\frac{144}{169}} = \frac{\sqrt{144}}{\sqrt{169}} = \frac{12}{13} \][/tex]

Since we assume [tex]\(\theta\)[/tex] is in the first quadrant (where both sine and cosine are positive), we take the positive root.

Therefore,

[tex]\[ \sin(\theta) = \frac{12}{13} \][/tex]