× The formulas which will be on the exam Reciprocal Identities Pythagorean Identities Even-Odd Identities Double Angle Identities Half Angle Identities Unit Circle Graphs of Circles Graphs of Cardioids Graphs of Limac̀§ons Graphs of Lemniscates Graphs of Rose Curves Graphs of Spiral Curves Graphs of Ellipses
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My name is Han Yin, and I have developed this website as a resource to facilitate the review of key concepts and it is not fully completed. Feel free to email me at hanyin@ku.edu if there are any errors or suggestions for improvement.

Trigonometry Identities

Those will be on the Midterm

Those will be provided in the exam. You do not need to memorize them. However, you need to know how to use them.

Sum and Difference of Angles Identities

\[ \begin{aligned} &\sin(x + y) = \sin(x) \cos(y) + \cos(x) \sin(y) \\ &\sin(x - y) = \sin(x) \cos(y) - \cos(x) \sin(y) \\ &\cos(x + y) = \cos(x) \cos(y) - \sin(x) \sin(y) \\ &\cos(x - y) = \cos(x) \cos(y) + \sin(x) \sin(y) \\ \end{aligned} \]

The Double-Angle Identities

\[ \sin(2x) = 2 \sin(x) \cos(x) \qquad \cos(2x) = \cos^2(x) - \sin^2(x) \]

Power-Reducing Formulas: (Half-Angle Identities)

\[ \sin^2(x) = \frac{1 - \cos(2x)}{2} \qquad \cos^2(x) = \frac{1 + \cos(2x)}{2} \]

Product to Sum or Difference Identities

\[ \begin{aligned} &\sin(u) \cos(v) = \frac{1}{2} \left( \sin(u + v) + \sin(u - v) \right) \\ &\cos(u) \cos(v) = \frac{1}{2} \left( \cos(u + v) + \cos(u - v) \right) \\ &\sin(u) \sin(v) = \frac{1}{2} \left( \cos(u - v) - \cos(u + v) \right) \\ \end{aligned} \]

Sum to Product Identities

\[ \begin{aligned} &\sin(x) + \sin(y) = 2 \sin\left(\frac{x + y}{2}\right) \cos\left(\frac{x - y}{2}\right) \quad \sin(x) - \sin(y) = 2 \cos\left(\frac{x + y}{2}\right) \sin\left(\frac{x - y}{2}\right) \\ &\cos(x) + \cos(y) = 2 \cos\left(\frac{x + y}{2}\right) \cos\left(\frac{x - y}{2}\right) \quad \cos(x) - \cos(y) = -2 \sin\left(\frac{x + y}{2}\right) \sin\left(\frac{x - y}{2}\right) \end{aligned} \]

Law of Sine

\[ \frac{\sin(A)}{a} = \frac{\sin(B)}{b} = \frac{\sin(C)}{c} \]

Law of Cosine

\[ c^2 = a^2 + b^2 - 2ab \cos(C) \]

Those will not be on the Midterm

The following are the trigonometric identities that we went over in class.

Reciprocal Identities

\[ \sin(\theta) = \frac{1}{\csc(\theta)}, \qquad \cos(\theta) = \frac{1}{\sec(\theta)}, \qquad \tan(\theta) = \frac{1}{\cot(\theta)}, \qquad \csc(\theta) = \frac{1}{\sin(\theta)}, \qquad \sec(\theta) = \frac{1}{\cos(\theta)}, \qquad \cot(\theta) = \frac{1}{\tan(\theta)}. \]


Pythagorean Identities

\[ \sin^2(\theta) + \cos^2(\theta) = 1, \quad 1 + \tan^2(\theta) = \sec^2(\theta), \quad 1 + \cot^2(\theta) = \csc^2(\theta). \]


Even-Odd Identities

\[ \sin(-\theta) = -\sin(\theta), \quad \cos(-\theta) = \cos(\theta), \quad \tan(-\theta) = -\tan(\theta), \quad \csc(-\theta) = -\csc(\theta), \quad \sec(-\theta) = \sec(\theta), \quad \cot(-\theta) = -\cot(\theta). \]


Double Angle Identities

\[ \tan(2\theta) = \frac{2\tan(\theta)}{1 - \tan^2(\theta)} \]


Half Angle Identities

\[ \sin\left(\frac{\theta}{2}\right) = \pm \sqrt{\frac{1 - \cos(\theta)}{2}}, \quad \cos\left(\frac{\theta}{2}\right) = \pm \sqrt{\frac{1 + \cos(\theta)}{2}}, \quad \tan\left(\frac{\theta}{2}\right) = \pm \sqrt{\frac{1 - \cos(\theta)}{1 + \cos(\theta)}}. \]


Unit Circle

The unit circle is a circle with a radius of 1. It is used to define the trigonometric functions of any angle.

Unit Circle with angles and coordinates

Trigonometric Functions Table

Function Midline Amplitude Vertical Asymptote Period Phase Shift
\( A \cos(Bx - C) + D \) \( y = D \) \( |A| \) No \( \frac{2\pi}{|B|} \) \( \frac{C}{B} \)
\( A \sin(Bx - C) + D \) \( y = D \) \( |A| \) No \( \frac{2\pi}{|B|} \) \( \frac{C}{B} \)
\( A \tan(Bx - C) + D \) \( y = D \) \(|A|\) For \( \tan \): \( \frac{\pi}{2B} + \frac{C}{B} + \frac{\pi k}{B} \) \( \frac{\pi}{|B|} \) \( \frac{C}{B} \)
\( A \cot(Bx - C) + D \) \( y = D \) \(|A|\) \( \frac{\pi}{B} + \frac{C}{B} + \frac{\pi k}{B} \) \( \frac{\pi}{|B|} \) \( \frac{C}{B} \)
\( A \sec(Bx - C) + D \) \( y = D \) \( |A| \) \( \frac{\pi}{2B} + \frac{C}{B} + \frac{\pi k}{B} \) \( \frac{2\pi}{|B|} \) \( \frac{C}{B} \)
\( A \csc(Bx - C) + D \) \( y = D \) \( |A| \) \( \frac{\pi}{B} + \frac{C}{B} + \frac{\pi k}{B} \) \( \frac{2\pi}{|B|} \) \( \frac{C}{B} \)

Inverse Functions

Function Domain Range
\( \arcsin(x) \) \( -1 \leq x \leq 1 \) \( -\frac{\pi}{2} \leq y \leq \frac{\pi}{2} \)
\( \arccos(x) \) \( -1 \leq x \leq 1 \) \( 0 \leq y \leq \pi \)
\( \arctan(x) \) \( -\infty \lt x \lt \infty \) \( -\frac{\pi}{2} \lt y \lt \frac{\pi}{2} \)

Graphs of Circles


Graphs of Cardioids


Graphs of Limac̀§ons


Graphs of Lemniscates


Graphs of Rose Curves

Graphs of Spiral Curves

Graphs of Ellipses (1)

Graphs of Ellipses (2)

Graphs of Hyperbola

Graphs of Hyperbola centering at \((0, 0)\)

\[\frac{x^2}{a^2} - \frac{y^2}{b^2} = 1\]

The length of the Transverse axis is \(2a\).

The coordinates of the vertices are \((\pm a, 0)\).

The length of the conjugate axis is \(2b\).

The coordinates of the co-vertices are \((0, \pm b)\).

The distance between of the foci are \((\pm c, 0)\), where \(c = \sqrt{a^2 + b^2}\).

The equations of the asymptote are \(y = \pm \frac{b}{a}x\).

Graphs of Hyperbola centering at \((0, 0)\)

\[\frac{y^2}{a^2} - \frac{x^2}{b^2} = 1\]

The length of the Transverse axis is \(2a\).

The coordinates of the vertices are \((0, \pm a)\).

The length of the conjugate axis is \(2b\).

The coordinates of the co-vertices are \((\pm b, 0)\).

The coordinates of the foci are \((0, \pm c)\), where \(c = \sqrt{a^2 + b^2}\).

The distance between of the foci are \(2c\).

The equations of the asymptote are \(y = \pm \frac{a}{b}x\).

Graphs of Hyperbola centering at \((h, k)\)

\[\frac{(x-h)^2}{a^2} - \frac{(y-k)^2}{b^2} = 1\]

Graphs of Hyperbola centering at \((h, k)\)

\[\frac{(y-k)^2}{a^2} - \frac{(x-h)^2}{b^2} = 1\]

Graphs of Parabola

\[y^2 = 4px\]

\[x^2 = 4py\]