Select the correct answer.

If [tex]\cos (\theta)=\frac{3}{10}[/tex], what is [tex]\sin (\theta)[/tex]?

A. [tex]\frac{\sqrt{7}}{100}[/tex]
B. [tex]\frac{7}{10}[/tex]
C. [tex]\frac{\sqrt{91}}{10}[/tex]
D. [tex]\frac{91}{100}[/tex]



Answer :

To determine [tex]\(\sin(\theta)\)[/tex] given that [tex]\(\cos(\theta) = \frac{3}{10}\)[/tex], we can utilize the Pythagorean identity in trigonometry, which states:

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

Given:
[tex]\[ \cos(\theta) = \frac{3}{10} \][/tex]

First, we'll find [tex]\(\cos^2(\theta)\)[/tex]:

[tex]\[ \cos^2(\theta) = \left(\frac{3}{10}\right)^2 = \frac{9}{100} \][/tex]

Next, we substitute [tex]\(\cos^2(\theta)\)[/tex] into the Pythagorean identity to solve for [tex]\(\sin^2(\theta)\)[/tex]:

[tex]\[ \sin^2(\theta) + \frac{9}{100} = 1 \][/tex]

Subtract [tex]\(\frac{9}{100}\)[/tex] from both sides:

[tex]\[ \sin^2(\theta) = 1 - \frac{9}{100} = \frac{100}{100} - \frac{9}{100} = \frac{91}{100} \][/tex]

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

[tex]\[ \sin(\theta) = \sqrt{\frac{91}{100}} = \frac{\sqrt{91}}{10} \][/tex]

Therefore, the correct answer is:

C. [tex]\(\frac{\sqrt{91}}{10}\)[/tex]