Homework

Find the Value of Cosine on the Unit Circle

$$\text{Given the unit circle, we need to find the value of } \cos(\theta) \text{ where } \theta \text{ is an angle such that } 2\cos^2(\theta) + \cos(\theta) – 1 = 0.$$

$$\text{Step 1: Solve the quadratic equation} $$

$$2\cos^2(\theta) + \cos(\theta) – 1 = 0$$

$$\text{Using the quadratic formula } x = \frac{-b \pm \sqrt{b^2 – 4ac}}{2a}, \text{ where } a = 2, b = 1, \text{ and } c = -1$$

$$\cos(\theta) = \frac{-1 \pm \sqrt{1^2 – 4 \cdot 2 \cdot (-1)}}{2 \cdot 2} = \frac{-1 \pm \sqrt{1 + 8}}{4} = \frac{-1 \pm 3}{4}$$

$$\text{Thus, } \cos(\theta) = \frac{2}{4} = \frac{1}{2} \text{ or } \cos(\theta) = \frac{-4}{4} = -1.$$

$$\text{Therefore, the possible values of } \cos(\theta) \text{ are } \boxed{\frac{1}{2} \text{ and } -1}.$$

Find the cosine and sine of the angle 5π/6 using the unit circle

To find the cosine and sine of the angle $ \frac{5\pi}{6} $, we can use the unit circle. The angle $ \frac{5\pi}{6} $ is in the second quadrant, where the cosine is negative and the sine is positive.

First, find the reference angle:

$$ \text{Reference angle} = \pi – \frac{5\pi}{6} = \frac{\pi}{6} $$

For the angle $ \frac{\pi}{6} $, cosine and sine values are:

$$ \cos \left( \frac{\pi}{6} \right) = \frac{\sqrt{3}}{2} $$

$$ \sin \left( \frac{\pi}{6} \right) = \frac{1}{2} $$

Since $ \frac{5\pi}{6} $ is in the second quadrant:

$$ \cos \left( \frac{5\pi}{6} \right) = -\cos \left( \frac{\pi}{6} \right) = -\frac{\sqrt{3}}{2} $$

$$ \sin \left( \frac{5\pi}{6} \right) = \sin \left( \frac{\pi}{6} \right) = \frac{1}{2} $$

Find the sine, cosine, and tangent values for the angle π/4 on the unit circle

First, we need to recognize that the angle $\frac{\pi}{4}$ is equivalent to 45 degrees.

On the unit circle, the coordinates at $\frac{\pi}{4}$ are $(\frac{\sqrt{2}}{2}, \frac{\sqrt{2}}{2})$.

The sine value is the y-coordinate:

$$\sin(\frac{\pi}{4}) = \frac{\sqrt{2}}{2}$$

The cosine value is the x-coordinate:

$$\cos(\frac{\pi}{4}) = \frac{\sqrt{2}}{2}$$

The tangent value is the ratio of the sine and cosine values:

$$\tan(\frac{\pi}{4}) = \frac{\sin(\frac{\pi}{4})}{\cos(\frac{\pi}{4})} = 1$$

So, the sine, cosine, and tangent values for the angle $\frac{\pi}{4}$ are $\frac{\sqrt{2}}{2}$, $\frac{\sqrt{2}}{2}$, and 1, respectively.

Find the value of cos(θ) using the unit circle in the complex plane when θ = π/3

First, understand that on the unit circle, a point corresponding to an angle $\theta$ can be represented as $e^{i\theta} = \cos(\theta) + i\sin(\theta)$.

For $\theta = \frac{\pi}{3}$,

$e^{i\frac{\pi}{3}} = \cos\left(\frac{\pi}{3}\right) + i\sin\left(\frac{\pi}{3}\right)$.

We know that $\cos\left(\frac{\pi}{3}\right) = \frac{1}{2}$ and $\sin\left(\frac{\pi}{3}\right) = \frac{\sqrt{3}}{2}$.

Hence, $e^{i\frac{\pi}{3}} = \frac{1}{2} + i\frac{\sqrt{3}}{2}$.

So, $\cos\left(\frac{\pi}{3}\right) = \frac{1}{2}$.

Find the tangent of the angle \( \theta \) in the unit circle

Consider the unit circle, where the radius is 1. Let $ \theta $ be an angle in standard position.

The coordinates of the point on the unit circle at an angle $ \theta $ are $(\cos \theta, \sin \theta)$.

The tangent of the angle $ \theta $ is given by

$$ \tan \theta = \frac{\sin \theta}{\cos \theta} $$

For example, if $ \theta = 45^\circ $, then $ \sin 45^\circ = \cos 45^\circ = \frac{\sqrt{2}}{2} $.

Thus, $$ \tan 45^\circ = \frac{\frac{\sqrt{2}}{2}}{\frac{\sqrt{2}}{2}} = 1 $$

Find the angle given the coordinates on the unit circle

Given the coordinates (\(\frac{1}{2}\), \(\frac{\sqrt{3}}{2}\)) on the unit circle, find the corresponding angle in degrees.

The unit circle has a radius of 1. The coordinates \((x, y) \) on the unit circle can be represented as \((\cos \theta, \sin \theta)\).

So, we have:

\( \cos \theta = \frac{1}{2}\)

\( \sin \theta = \frac{\sqrt{3}}{2}\)

We need to find the angle \(\theta\) where both conditions hold true. Using the trigonometric values, we know:

\( \cos 60^\circ = \frac{1}{2}\)

\( \sin 60^\circ = \frac{\sqrt{3}}{2}\)

Thus, the angle is:

\( \theta = 60^\circ \)

Determine the quadrant of an angle on the unit circle

Given an angle of 150° on the unit circle, determine which quadrant it is in.

To determine which quadrant 150° is in, we note that if the angle is between 90° and 180°, it lies in the second quadrant.

Since 150° is between 90° and 180°, it is in the second quadrant.

So, the angle 150° is in the second quadrant.

What is the value of sin(30°) and cos(30°) on the unit circle?

First, we need to recall the values of sine and cosine for common angles on the unit circle. For $30°$ (or $\frac{\pi}{6}$ radians):

$$\sin(30°) = \frac{1}{2}$$

$$\cos(30°) = \frac{\sqrt{3}}{2}$$

Evaluate the cosine of an angle using the unit circle in the complex plane

$$ \text{Given an angle } \theta \text{, we need to find } \cos(\theta) \text{ using the unit circle in the complex plane.} $$

$$ \text{On the unit circle, the coordinates of a point } P \text{ corresponding to the angle } \theta \text{ are } (\cos(\theta), \sin(\theta)). $$

$$ \text{Thus, } \cos(\theta) \text{ is simply the x-coordinate.} $$

$$ \text{For example, if } \theta = \frac{\pi}{3}, \text{ the coordinates on the unit circle are } (\cos(\frac{\pi}{3}), \sin(\frac{\pi}{3})). $$

$$ \cos(\frac{\pi}{3}) = \frac{1}{2}. $$