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If \( \tan \theta=\frac{3}{4} \), fnd \( \cos \theta \)

Ask by Chambers Perkins. in Nigeria
Feb 17,2025

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Answer

\( \cos \theta = \frac{4}{5} \)

Solution

We start with the given:   tan θ = 3/4 Recall that tan θ is defined as sin θ divided by cos θ. That is:   tan θ = sin θ / cos θ One way to handle this is to imagine a right triangle where the side opposite the angle θ is 3 and the side adjacent is 4. By the Pythagorean theorem, the hypotenuse (h) is:   h = √(3² + 4²) = √(9 + 16) = √25 = 5 Since cosine is the ratio of the adjacent side to the hypotenuse, we get:   cos θ = 4/5 Note that unless otherwise specified, we assume θ is an acute angle, in which case cos θ is positive.

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Bonus Knowledge

To find \( \cos \theta \) when \( \tan \theta = \frac{3}{4} \), we can use the identity \( \tan \theta = \frac{\text{opposite}}{\text{adjacent}} \). Here, we can think of a right triangle where the opposite side is 3 and the adjacent side is 4. Using the Pythagorean theorem, we can find the hypotenuse \( h \): \[ h = \sqrt{3^2 + 4^2} = \sqrt{9 + 16} = \sqrt{25} = 5. \] Now, we can find \( \cos \theta \) using \( \cos \theta = \frac{\text{adjacent}}{\text{hypotenuse}} \): \[ \cos \theta = \frac{4}{5}. \] So, \( \cos \theta = \frac{4}{5} \).

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