Homework

Find the coordinates of the point on the unit circle at angle π/3 radians

To find the coordinates of the point on the unit circle at angle $\pi/3$ radians, we use the unit circle definitions. The unit circle is defined by the equation $x^2 + y^2 = 1$, where the coordinates $(x, y)$ correspond to $(\cos(\theta), \sin(\theta))$ for an angle $\theta$.

For $\theta = \pi/3$:

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

$$y = \sin(\pi/3) = \frac{\sqrt{3}}{2}$$

Thus, the coordinates are $\left( \frac{1}{2}, \frac{\sqrt{3}}{2} \right)$.

Given the unit circle, if the point (a, b) lies on the circle, find the value of sin(2θ), cos(2θ), and tan(2θ) where θ is the angle that corresponds to the point (a, b) Verify that these values satisfy the double angle identities

Given the point (a, b) on the unit circle, we know:

$$a = \cos \theta $$

$$b = \sin \theta $$

We need to find $\sin(2\theta)$, $\cos(2\theta)$, and $\tan(2\theta)$. Using the double angle identities:

$$ \sin(2\theta) = 2 \sin \theta \cos \theta $$

$$ \cos(2\theta) = \cos^2 \theta – \sin^2 \theta $$

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

By substituting a = cos θ and b = sin θ:

$$ \sin(2\theta) = 2ab $$

$$ \cos(2\theta) = a^2 – b^2 $$

$$ \tan(2\theta) = \frac{2b/a}{1 – b^2/a^2} = \frac{2b/a}{(a^2 – b^2)/a^2} = \frac{2ab}{a^2 – b^2} $$

Verification of double-angle identities:

$$ (2ab)^2 + (a^2 – b^2)^2 = 4a^2b^2 + a^4 – 2a^2b^2 + b^4 = a^4 + 2a^2b^2 + b^4 = (a^2 + b^2)^2 = 1 $$

Find the exact coordinates of a point on the unit circle given that the point is 7π/6 radians from the positive x-axis

To determine the coordinates of the point on the unit circle at an angle of $\frac{7\pi}{6}$ radians, we use the sine and cosine functions:

The x-coordinate (cosine) is:

$$\cos\left(\frac{7\pi}{6}\right) = \cos\left(\pi + \frac{\pi}{6}\right) = -\cos\left(\frac{\pi}{6}\right) = -\frac{\sqrt{3}}{2}$$

The y-coordinate (sine) is:

$$\sin\left(\frac{7\pi}{6}\right) = \sin\left(\pi + \frac{\pi}{6}\right) = -\sin\left(\frac{\pi}{6}\right) = -\frac{1}{2}$$

Thus, the exact coordinates are:

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

Find the sine and cosine values for the angle 30 degrees on the unit circle

To find the sine and cosine values for the angle $30^{\circ}$ on the unit circle, we use the known values of sine and cosine for common angles. The coordinates of the point on the unit circle at $30^{\circ}$ are $(\frac{\sqrt{3}}{2}, \frac{1}{2})$.

Therefore,

$$ \sin(30^{\circ}) = \frac{1}{2} $$

$$ \cos(30^{\circ}) = \frac{\sqrt{3}}{2} $$

Given a point on the unit circle with coordinates \((x, y)\), if the point corresponds to an angle \(\theta\) in standard position, find the angle \(\theta\) if \(x = -\frac{1}{2}\) State your answer in radians

Given the point on the unit circle with coordinates $(x, y)$, we need to find $\theta$ if $x = -\frac{1}{2}$.

Since $x = -\frac{1}{2}$ on the unit circle, we can use the cosine function to find the angle. So, $\cos(\theta) = -\frac{1}{2}$.

The angles that satisfy this equation are $\theta = \frac{2\pi}{3}$ and $\theta = \frac{4\pi}{3}$ in the interval $[0, 2\pi)$.

Hence, the angles $\theta$ corresponding to $x = -\frac{1}{2}$ are:

$$ \theta = \frac{2\pi}{3}, \frac{4\pi}{3} $$

What is the cosine and sine value of π/3 on the flipped unit circle?

To find the cosine and sine values of $$\frac{\pi}{3}$$ on the flipped unit circle, we start by recalling the standard unit circle values.

On the standard unit circle,

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

and

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

When flipping the unit circle over the x-axis, the sine value changes its sign:

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

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

Find the values of cos(θ) on the unit circle

Consider the unit circle where the radius is 1. Identify the angles $\theta$ where $\cos(\theta) = \frac{1}{2}$.

Step 1: Recall the unit circle and the corresponding cosine values for common angles.

Step 2: Evaluate the cosine values: $\cos(60^\circ) = \frac{1}{2}$ and $\cos(300^\circ) = \frac{1}{2}$.

Step 3: Convert these angles to radians: $60^\circ = \frac{\pi}{3}$ and $300^\circ = \frac{5\pi}{3}$.

Therefore, the values of $\theta$ where $\cos(\theta) = \frac{1}{2}$ are $\frac{\pi}{3}$ and $\frac{5\pi}{3}$.

Find the cosecant of an angle at 30 degrees on the unit circle

The unit circle value for sine at 30 degrees is $\frac{1}{2}$. The cosecant is the reciprocal of sine.

$$ \csc(30^{\circ}) = \frac{1}{\sin(30^{\circ})} = \frac{1}{\frac{1}{2}} = 2 $$

So, the cosecant of 30 degrees is 2.

Find the sine, cosine, and tangent of an angle on the unit circle at 45 degrees

To find the sine, cosine, and tangent of a $45^\circ$ angle, we start by remembering that on the unit circle:

$$\sin(45^\circ) = \frac{\sqrt{2}}{2}$$

$$\cos(45^\circ) = \frac{\sqrt{2}}{2}$$

$$\tan(45^\circ) = 1$$

Therefore, the sine, cosine, and tangent of $45^\circ$ are $\frac{\sqrt{2}}{2}$, $\frac{\sqrt{2}}{2}$, and $1$ respectively.

Find all circle equations that lie on the unit circle

The unit circle is defined by the equation:

$$x^2 + y^2 = 1$$

To find all circles that lie on the unit circle, we consider the general equation of a circle:

$$ (x – a)^2 + (y – b)^2 = r^2 $$

For the circle to lie on the unit circle, the radius of this circle must be zero, as any larger radius would extend beyond the unit circle. Therefore:

$$ r = 0 $$

Thus, the equation simplifies to a point:

$$ (x – a)^2 + (y – b)^2 = 0 $$

Expanding this gives:

$$ x = a, y = b $$

But since it must lie on the unit circle:

$$ a^2 + b^2 = 1 $$

So, all such points (a, b) lie on the unit circle.

Therefore, the equations of all circles on the unit circle are:

$$ (x – a)^2 + (y – b)^2 = 0 $$ where $$ a^2 + b^2 = 1 $$