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Consider this equation:

[tex]\cos (\theta)=\frac{\sqrt{11}}{5}[/tex]

If [tex]\theta[/tex] is an angle in quadrant [tex]I[/tex], what is the value of [tex]\sin (\theta)[/tex]?

A. [tex]\frac{\sqrt{14}}{5}[/tex]
B. [tex]\frac{\sqrt{154}}{11}[/tex]
C. [tex]-\frac{\sqrt{184}}{11}[/tex]
D. [tex]-\frac{\sqrt{14}}{5}[/tex]


Sagot :

To determine the value of [tex]\(\sin(\theta)\)[/tex] given that [tex]\(\cos(\theta) = \frac{\sqrt{11}}{5}\)[/tex] and [tex]\(\theta\)[/tex] is an angle in quadrant I, we can use the Pythagorean identity. This identity states that:

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

We are given [tex]\(\cos(\theta) = \frac{\sqrt{11}}{5}\)[/tex]. First, we will square [tex]\(\cos(\theta)\)[/tex]:

[tex]\[ \cos^2(\theta) = \left( \frac{\sqrt{11}}{5} \right)^2 = \frac{11}{25} \][/tex]

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

[tex]\[ \sin^2(\theta) = 1 - \cos^2(\theta) = 1 - \frac{11}{25} = \frac{25}{25} - \frac{11}{25} = \frac{14}{25} \][/tex]

Now, we need to find the value of [tex]\(\sin(\theta)\)[/tex]:

[tex]\[ \sin(\theta) = \sqrt{\sin^2(\theta)} = \sqrt{\frac{14}{25}} = \frac{\sqrt{14}}{5} \][/tex]

Since [tex]\(\theta\)[/tex] is in quadrant I, both [tex]\(\sin(\theta)\)[/tex] and [tex]\(\cos(\theta)\)[/tex] are positive. Therefore, the value of [tex]\(\sin(\theta)\)[/tex] is:

[tex]\[ \sin(\theta) = \frac{\sqrt{14}}{5} \][/tex]

So the correct answer is:

A. [tex]\(\frac{\sqrt{14}}{5}\)[/tex]
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