Homework

Find the value of tan(θ) on the unit circle where θ=150°

To find $\tan(150^\circ)$, we first note that $150^\circ$ can be written as $180^\circ – 30^\circ$.

The reference angle here is $30^\circ$.

Since $\tan\theta$ is negative in the second quadrant:

$$\tan(150^\circ) = -\tan(30^\circ)$$

We know that $\tan(30^\circ) = \frac{1}{\sqrt{3}}\ or \ \frac{\sqrt{3}}{3}$.

Therefore,

$$\tan(150^\circ) = -\frac{1}{\sqrt{3}}\ or \ -\frac{\sqrt{3}}{3}$$

Find the coordinates on the unit circle for an angle of \(\frac{\pi}{3}\) radians

To find the coordinates of an angle of $\frac{\pi}{3}$ radians on the unit circle, we use the cosine and sine values of the angle.

The cosine of $\frac{\pi}{3}$ is $\frac{1}{2}$.

The sine of $\frac{\pi}{3}$ is $\frac{\sqrt{3}}{2}$.

Therefore, the coordinates are:

$$\left( \frac{1}{2}, \frac{\sqrt{3}}{2} \right)$$

Find the values of cos(θ) and sin(θ) for θ = 5π/4

To find the values of $\cos(\theta)$ and $\sin(\theta)$ for $\theta = \frac{5\pi}{4}$, we start by locating the angle on the unit circle. The angle $\frac{5\pi}{4}$ is in the third quadrant.

In the third quadrant, both sine and cosine values are negative. The reference angle for $\frac{5\pi}{4}$ is $\pi/4$, for which the cosine and sine values are both $\frac{\sqrt{2}}{2}$.

Therefore:

$$\cos\left(\frac{5\pi}{4}\right) = -\frac{\sqrt{2}}{2}$$

$$\sin\left(\frac{5\pi}{4}\right) = -\frac{\sqrt{2}}{2}$$

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

Given an angle \( \theta \) in the complex plane, the unit circle can be used to find the cosine of the angle. The cosine of the angle \( \theta \) is the x-coordinate of the point where the terminal side of the angle intersects the unit circle.

Let’s consider \( \theta = \frac{\pi}{4} \), find \( \cos(\theta) \).

On the unit circle, the coordinates of the point at angle \( \frac{\pi}{4} \) are \( \left( \cos \left( \frac{\pi}{4} \right), \sin \left( \frac{\pi}{4} \right) \right) \).

Since \( \frac{\pi}{4} \) is a 45-degree angle, the coordinates are \( \left( \frac{\sqrt{2}}{2}, \frac{\sqrt{2}}{2} \right) \).

Thus, the cosine of \( \frac{\pi}{4} \) is:

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

Convert the point on the unit circle given in Cartesian coordinates (sqrt(3)/2, 1/2) to its corresponding angle in degrees and radians, and verify the solution by converting the angle back to Cartesian coordinates

We are given the point $(\sqrt{3}/2, 1/2)$ on the unit circle. To find the corresponding angle, we use the following trigonometric relationships:

$$x = \cos(\theta)$$

$$y = \sin(\theta)$$

Thus, we have:

$$\cos(\theta) = \sqrt{3}/2$$

$$\sin(\theta) = 1/2$$

For the angle $\theta$ that satisfies these equations, we recognize that these are standard values. The angle $\theta$ is $30^{\circ}$ or $\pi/6$ radians.

To verify, we will convert $30^{\circ}$ back to Cartesian coordinates:

$$\cos(30^{\circ}) = \sqrt{3}/2, \sin(30^{\circ}) = 1/2$$

Thus, the point $(\cos(30^{\circ}), \sin(30^{\circ})) = (\sqrt{3}/2, 1/2)$ matches the given point. Therefore, $\theta = 30^{\circ}$ or $\pi/6$ radians.

Given a point on the unit circle, determine the coordinates and verify the trigonometric identities

Let’s consider a point $P(\cos\theta, \sin\theta)$ on the unit circle where $\theta = \frac{5\pi}{6}$. To find the coordinates and verify trigonometric identities:

First, we calculate the coordinates:

$$P = (\cos \frac{5\pi}{6}, \sin \frac{5\pi}{6})$$

Using the unit circle, we know:

$$\cos \frac{5\pi}{6} = -\frac{\sqrt{3}}{2}$$

$$\sin \frac{5\pi}{6} = \frac{1}{2}$$

Thus, the coordinates are:

$$P = \left(-\frac{\sqrt{3}}{2}, \frac{1}{2}\right)$$

Next, we verify the Pythagorean identity:

$$\cos^2 \theta + \sin^2 \theta = 1$$

Substituting in the values, we get:

$$\left(-\frac{\sqrt{3}}{2}\right)^2 + \left(\frac{1}{2}\right)^2 = \frac{3}{4} + \frac{1}{4} = 1$$

Which confirms that the point lies on the unit circle.

What is the cosine of the angle π/3 on the unit circle?

To find the cosine of the angle \( \frac{\pi}{3} \) on the unit circle, we need to locate this angle on the circle.

The angle \( \frac{\pi}{3} \) corresponds to 60 degrees.

On the unit circle, the coordinates of the point at angle \( \frac{\pi}{3} \) are \( \left( \frac{1}{2}, \frac{\sqrt{3}}{2} \right) \).

The cosine of an angle is the x-coordinate of the corresponding point on the unit circle.

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

Find all angles θ between 0 and 2π such that cos(θ) = -1/2

To find the angles $\theta$ such that $\cos(\theta) = -\frac{1}{2}$, we start by identifying the quadrants where $\cos(\theta)$ is negative. Cosine is negative in the second and third quadrants.

First, we find the reference angle:

$$\cos^{-1}\left(\frac{1}{2}\right) = \frac{\pi}{3}$$

Now, we find the angles in the second and third quadrants:

Second quadrant: $$\pi – \frac{\pi}{3} = \frac{2\pi}{3}$$

Third quadrant: $$\pi + \frac{\pi}{3} = \frac{4\pi}{3}$$

Thus, the angles are $\frac{2\pi}{3}$ and $\frac{4\pi}{3}$.

Find the exact values of sine and cosine for the angle 5π/4 using the unit circle

To find the exact values of sine and cosine for the angle $\frac{5\pi}{4}$, we start by determining in which quadrant the angle lies.

The angle $\frac{5\pi}{4}$ is in the third quadrant because $\frac{5\pi}{4} > \pi$ and $\frac{5\pi}{4} < \frac{3\pi}{2}$.

In the third quadrant, both sine and cosine are negative.

The reference angle for $\frac{5\pi}{4}$ is $\frac{\pi}{4}$.

We know that $\sin(\frac{\pi}{4}) = \frac{\sqrt{2}}{2}$ and $\cos(\frac{\pi}{4}) = \frac{\sqrt{2}}{2}$.

Hence, for the third quadrant:

$$\sin(\frac{5\pi}{4}) = -\frac{\sqrt{2}}{2}$$

$$\cos(\frac{5\pi}{4}) = -\frac{\sqrt{2}}{2}$$

Find the coordinates of the points where the unit circle intersects the x-axis

$$\text{The unit circle has the equation } x^2 + y^2 = 1.$$

$$\text{To find the intersection with the x-axis, we set } y = 0.$$

$$x^2 + 0^2 = 1$$

$$x^2 = 1$$

$$x = \pm 1.$$

$$\text{Thus, the coordinates are } (1, 0) \text{ and } (-1, 0).$$