Homework

Calculate the value of tan(θ) at θ = 45° using the unit circle

To calculate $ \tan(\theta) $ at $ \theta = 45° $ using the unit circle, we note that at $ 45° $, the coordinates on the unit circle are $ \left( \frac{\sqrt{2}}{2}, \frac{\sqrt{2}}{2} \right) $.

The formula for $ \tan(\theta) $ is:

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

Since at $ \theta = 45° $:

$$ \sin(45°) = \frac{\sqrt{2}}{2} $$

$$ \cos(45°) = \frac{\sqrt{2}}{2} $$

The value of $ \tan(45°) $ is:

$$ \tan(45°) = \frac{\frac{\sqrt{2}}{2}}{\frac{\sqrt{2}}{2}} = 1 $$

Determine the value of cos(θ) when sin(θ) = 1/2 in the unit circle

In the unit circle, when $ \sin(\theta) = \frac{1}{2} $, we need to determine $ \cos(\theta) $.

Since $ \sin(\theta) $ relates to the y-coordinate and $ \cos(\theta) $ relates to the x-coordinate in the unit circle, we use the Pythagorean identity:

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

Given $ \sin(\theta) = \frac{1}{2} $, we can substitute:

$$ \left(\frac{1}{2}\right)^2 + \cos^2(\theta) = 1 $$

$$ \frac{1}{4} + \cos^2(\theta) = 1 $$

$$ \cos^2(\theta) = 1 – \frac{1}{4} $$

$$ \cos^2(\theta) = \frac{3}{4} $$

Taking the square root of both sides, we get:

$$ \cos(\theta) = \pm \sqrt{\frac{3}{4}} $$

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

Given a point on the unit circle at angle θ, determine the coordinates of the point and the angle θ in radians

The unit circle is defined as the set of points (x,y) such that $x^2 + y^2 = 1$. For a point on the unit circle at an angle $ \theta $, the coordinates of the point are $(\cos(\theta),\sin(\theta))$.

For example, if $ \theta = \frac{\pi}{4} $, then:

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

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

Thus, the coordinates of the point are $\left( \frac{\sqrt{2}}{2}, \frac{\sqrt{2}}{2} \right)$. So, the answer is $\theta = \frac{\pi}{4}$ rad.

Find the value of cos(θ) and sin(θ) when θ is an angle on the unit circle

To find the values of $\cos(\theta)$ and $\sin(\theta)$ when $\theta$ is an angle on the unit circle, we use the coordinates of the corresponding point on the unit circle.

\n

For example, if $\theta = \frac{5\pi}{6}$, then the point on the unit circle is $(-\frac{\sqrt{3}}{2}, \frac{1}{2})$.

\n

Therefore:

\n

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

\n

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

What are some effective methods to memorize the angles and coordinates on the unit circle?

One effective method to memorize the unit circle is to understand the symmetries in the circle. The unit circle is symmetrical across the x-axis, y-axis, and the origin. Hence, if you memorize one quadrant, you can derive the other quadrants by using these symmetries. For example, the angle $ \frac{\pi}{4} $ has coordinates $ (\frac{\sqrt{2}}{2}, \frac{\sqrt{2}}{2}) $. The corresponding angles in other quadrants can be obtained by changing the signs of the coordinates.

Another method is to use mnemonic devices. For example, the coordinates for the angles $ 0, \frac{\pi}{6}, \frac{\pi}{4}, \frac{\pi}{3}, \frac{\pi}{2} $ are respectively $ (1, 0), (\frac{\sqrt{3}}{2}, \frac{1}{2}), (\frac{\sqrt{2}}{2}, \frac{\sqrt{2}}{2}), (\frac{1}{2}, \frac{\sqrt{3}}{2}), (0, 1) $. You can memorize them by associating each angle with its coordinate pair.

Additionally, you can use the fact that the unit circle is related to the trigonometric functions $ \sin $ and $ \cos $. For each angle, the x-coordinate is $ \cos \theta $ and the y-coordinate is $ \sin \theta $. This relationship can help you derive the coordinates if you know the sine and cosine values for common angles.

Calculate the exact values of sin and cos at θ = 5π/6

To find the exact values of $ \sin $ and $ \cos $ at $ \theta = \frac{5\pi}{6} $, we use the unit circle.

First, find the reference angle:

$$ \theta_{ref} = \pi – \frac{5\pi}{6} = \frac{\pi}{6} $$

Using the reference angle $ \frac{\pi}{6} $, we know the exact values for sine and cosine are:

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

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

Since $ \theta = \frac{5\pi}{6} $ is in the second quadrant, sine is positive, and cosine is negative.

Therefore:

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

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

Find the tangent of an angle on a unit circle

Given an angle $ \theta $ on a unit circle, the tangent of the angle is defined as the ratio of the sine to the cosine of the angle.

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

For instance, if $ \theta = \frac{\pi}{4} $:

$$ \tan\left(\frac{\pi}{4}\right) = \frac{\sin\left(\frac{\pi}{4}\right)}{\cos\left(\frac{\pi}{4}\right)} = \frac{\frac{\sqrt{2}}{2}}{\frac{\sqrt{2}}{2}} = 1 $$

Thus, the tangent of $ \frac{\pi}{4} $ is 1.

Find the exact values of trigonometric functions at angles on the unit circle

Consider the angles $ \theta = \frac{5\pi}{6} $, $ \theta = \frac{7\pi}{4} $, and $ \theta = \frac{2\pi}{3} $ on the unit circle. We need to find the exact values of $ \sin(\theta) $, $ \cos(\theta) $, and $ \tan(\theta) $ for each angle.

For $ \theta = \frac{5\pi}{6} $:

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

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

$$ \tan\left( \frac{5\pi}{6} \right) = -\frac{1}{\sqrt{3}} $$

For $ \theta = \frac{7\pi}{4} $:

$$ \sin\left( \frac{7\pi}{4} \right) = -\frac{\sqrt{2}}{2} $$

$$ \cos\left( \frac{7\pi}{4} \right) = \frac{\sqrt{2}}{2} $$

$$ \tan\left( \frac{7\pi}{4} \right) = -1 $$

For $ \theta = \frac{2\pi}{3} $:

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

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

$$ \tan\left( \frac{2\pi}{3} \right) = -\sqrt{3} $$

Find the sine and cosine values at specific angles on the unit circle

To find the sine and cosine values at specific angles on the unit circle, we use the definitions of sine and cosine in terms of the unit circle.

For example, at an angle of 30 degrees (or $\frac{\pi}{6}$ radians):

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

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

Find the value of tan(240) using the unit circle

To find the value of $\tan(240)$ using the unit circle, we first determine the corresponding point on the unit circle for an angle of 240 degrees.

240 degrees is in the third quadrant, where the tangent function is positive.

We can subtract 180 degrees to find the reference angle:

$$240^{\circ} – 180^{\circ} = 60^{\circ}$$

The reference angle is 60 degrees. The coordinates for 60 degrees on the unit circle are $\left( \frac{1}{2}, \frac{\sqrt{3}}{2} \right)$.

Since we are in the third quadrant, both coordinates are negative:

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

The formula for tangent is:

$$ \tan(\theta) = \frac{y}{x} $$

Thus,

$$ \tan(240^{\circ}) = \frac{-\frac{\sqrt{3}}{2}}{-\frac{1}{2}} = \sqrt{3} $$