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Activity [tex]$8d$[/tex]

1. Given that [tex]$\sin (\theta) = \frac{3}{5}$[/tex] and [tex]$\cos (\theta) = \frac{4}{5}$[/tex], find [tex]$\sin (2\theta)$[/tex] and [tex]$\cos (2\theta)$[/tex].


Sagot :

Of course! Let's solve the problem step by step, making use of trigonometric identities.

Given:
[tex]\[ \sin(\theta) = \frac{3}{5} \quad \text{and} \quad \cos(\theta) = \frac{4}{5} \][/tex]

### Finding [tex]\(\sin(2\theta)\)[/tex]

We will use the double-angle formula for sine:
[tex]\[ \sin(2\theta) = 2 \sin(\theta) \cos(\theta) \][/tex]

Substitute the given values:
[tex]\[ \sin(2\theta) = 2 \left(\frac{3}{5}\right) \left(\frac{4}{5}\right) \][/tex]

Calculate the product inside the parentheses first:
[tex]\[ \frac{3}{5} \times \frac{4}{5} = \frac{12}{25} \][/tex]

Then multiply by 2:
[tex]\[ 2 \times \frac{12}{25} = \frac{24}{25} \][/tex]

Therefore,
[tex]\[ \sin(2\theta) = \frac{24}{25} = 0.96 \][/tex]

### Finding [tex]\(\cos(2\theta)\)[/tex]

We will use the double-angle formula for cosine:
[tex]\[ \cos(2\theta) = \cos^2(\theta) - \sin^2(\theta) \][/tex]

First, compute [tex]\(\cos^2(\theta)\)[/tex] and [tex]\(\sin^2(\theta)\)[/tex]:
[tex]\[ \cos^2(\theta) = \left(\frac{4}{5}\right)^2 = \frac{16}{25} \][/tex]
[tex]\[ \sin^2(\theta) = \left(\frac{3}{5}\right)^2 = \frac{9}{25} \][/tex]

Then subtract [tex]\(\sin^2(\theta)\)[/tex] from [tex]\(\cos^2(\theta)\)[/tex]:
[tex]\[ \cos(2\theta) = \frac{16}{25} - \frac{9}{25} = \frac{7}{25} \][/tex]

Therefore,
[tex]\[ \cos(2\theta) = \frac{7}{25} = 0.28 \][/tex]

Putting it all together, we find:
[tex]\[ \sin(2\theta) = 0.96 \quad \text{and} \quad \cos(2\theta) = 0.28 \][/tex]

So, the values are:
[tex]\[ \sin(2\theta) = 0.96 \quad \text{and} \quad \cos(2\theta) = 0.28000000000000014 \][/tex]