High School Math : High School Math

Study concepts, example questions & explanations for High School Math

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Example Questions

Example Question #1 : Trigonometry

If the polar coordinates of a point are \(\displaystyle \left (2,\frac{-\pi}{4} \right )\), then what are its rectangular coordinates?

Possible Answers:

\(\displaystyle (2,-\sqrt2)\)

\(\displaystyle (\sqrt2,\sqrt2)\)

\(\displaystyle (\sqrt2,-\sqrt2)\)

\(\displaystyle (2,2)\)

\(\displaystyle (-\sqrt2,-\sqrt2)\)

Correct answer:

\(\displaystyle (\sqrt2,-\sqrt2)\)

Explanation:

The polar coordinates of a point are given as \(\displaystyle (r,\theta )\), where r represents the distance from the point to the origin, and \(\displaystyle \theta\) represents the angle of rotation. (A negative angle of rotation denotes a clockwise rotation, while a positive angle denotes a counterclockwise rotation.)

The following formulas are used for conversion from polar coordinates to rectangular (x, y) coordinates.

\(\displaystyle x=r\cos\theta\)

\(\displaystyle y=r\sin\theta\)

In this problem, the polar coordinates of the point are  \(\displaystyle \left (2,\frac{-\pi}{4} \right )\), which means that \(\displaystyle r = 2\) and \(\displaystyle \theta=-\frac{\pi}{4}\). We can apply the conversion formulas to find the values of x and y.

\(\displaystyle x=r\cos\theta=2\cos\left (\frac{-\pi}{4} \right )=2\cdot \frac{\sqrt2}{2}= \sqrt{2}\)

\(\displaystyle y=r\sin\theta=2\sin\left (\frac{-\pi}{4} \right )=2\cdot \frac{-\sqrt2}{2}= -\sqrt{2}\)

The rectangular coordinates are \(\displaystyle (\sqrt2,-\sqrt2)\).

The answer is \(\displaystyle (\sqrt2,-\sqrt2)\).

Example Question #1 : Understanding Sine, Cosine, And Tangent

Triangle

What is the \(\displaystyle \sin C\)?

Possible Answers:

\(\displaystyle \frac{AC}{AB}\)

\(\displaystyle \frac{AB}{BC}\)

\(\displaystyle \frac{AB}{AC}\)

\(\displaystyle \frac{BC}{AB}\)

 

\(\displaystyle \frac{BC}{AC}\)

Correct answer:

\(\displaystyle \frac{AB}{AC}\)

Explanation:

\(\displaystyle \sin X = \frac{OPPOSITE}{HYPOTENUSE}\)

 

\(\displaystyle \sin C = \frac{AB}{AC}\)

Example Question #1 : Graphing The Sine And Cosine Functions

Triangle

In the right triangle above, which of the following expressions gives the length of y?

Possible Answers:

\(\displaystyle x\cos\theta\)

\(\displaystyle x\tan\theta\)

\(\displaystyle x\sin\theta\)

\(\displaystyle \frac{\sin(x)}{\theta}\)

\(\displaystyle \cos(x\times \theta)\)

Correct answer:

\(\displaystyle x\cos\theta\)

Explanation:

\(\displaystyle \cos\theta\) is defined as the ratio of the adjacent side to the hypotenuse, or in this case \(\displaystyle \frac{y}{x}\). Solving for y gives the correct expression.

Example Question #2 : Understanding Sine, Cosine, And Tangent

What is the cosine of \(\displaystyle 30^\circ\)?

Possible Answers:

\(\displaystyle \sqrt{3}\)

\(\displaystyle \frac{1}{3}\)

\(\displaystyle \frac{1}{2}\)

\(\displaystyle \frac{2\sqrt{3}}{3}\)

\(\displaystyle \frac{\sqrt{3}}{2}\)

Correct answer:

\(\displaystyle \frac{\sqrt{3}}{2}\)

Explanation:

The pattern for the side of a \(\displaystyle 30:60:90\) triangle is \(\displaystyle x:x\sqrt{3}:2x\).

 Since \(\displaystyle \cos=\frac{\text{adjacent}}{\text{hypotenuse}}\), we can plug in our given values.

\(\displaystyle \cos=\frac{\text{adjacent}}{\text{hypotenuse}}\)

\(\displaystyle \cos=\frac{x\sqrt{3}}{2x}\)

Notice that the \(\displaystyle x\)'s cancel out.

\(\displaystyle \cos=\frac{\sqrt{3}}{2}\)

Example Question #1 : Trigonometry

If \(\displaystyle sin(x)=0.5\), what is \(\displaystyle sin(8x)\) if \(\displaystyle x\) is between \(\displaystyle 0\) and \(\displaystyle 2\pi\)?

Possible Answers:

\(\displaystyle 0.5\)

\(\displaystyle -1.5\)

\(\displaystyle -\frac{\sqrt{3}}{2}\)

\(\displaystyle \frac{\sqrt{3}}{2}\)

\(\displaystyle -0.5\)

Correct answer:

\(\displaystyle -\frac{\sqrt{3}}{2}\)

Explanation:

Recall that \(\displaystyle sin(\frac{\pi}{6}) =0.5\).

Therefore, we are looking for \(\displaystyle sin(8*\frac{\pi}{6})\) or \(\displaystyle sin(\frac{4\pi}{3})\).

Now, this has a reference angle of \(\displaystyle \frac{\pi}{3}\), but it is in the third quadrant. This means that the value will be negative. The value of \(\displaystyle sin(\frac{\pi}{3})\) is \(\displaystyle \frac{\sqrt{3}}{2}\). However, given the quadrant of our angle, it will be \(\displaystyle -\frac{\sqrt{3}}{2}\).

Example Question #1 : Trigonometry

An angle has a cosine of \(\displaystyle \frac{4}{5}\). What will its cosecant be?

Possible Answers:

\(\displaystyle \frac{4}{3}\)

\(\displaystyle \frac{5}{3}\)

\(\displaystyle \frac{3}{4}\)

\(\displaystyle \frac{5}{4}\)

\(\displaystyle \frac{3}{5}\)

Correct answer:

\(\displaystyle \frac{5}{3}\)

Explanation:

The problem tells us that the cosine of the angle will be \(\displaystyle \frac{4}{5}\). Cosine is the adjacent over the hypotenuse. From here we can use the Pythaogrean theorem:

\(\displaystyle \text{Opposite}^2+\text{Adjacent}^2=\text{Hypotenuse}^2\)

\(\displaystyle O^2+4^2=5^2\)

\(\displaystyle O^2+16=25\)

\(\displaystyle O^2=9\)

\(\displaystyle \sqrt{O^2}=\sqrt{9}\)

\(\displaystyle O=3\)

Now we know our opposite, adjacent, and hypotenuse.

The cosecant is \(\displaystyle \csc=\frac{\text{Hypotenuse}}{\text{Opposite}}\).

From here we can plug in our given values.

\(\displaystyle \csc=\frac{5}{3}\)

Example Question #3 : Trigonometry

Which of these is equal to \(\displaystyle \frac{\text{hypotenuse}}{\text{adjacent}}\) for angle \(\displaystyle x\)?

Possible Answers:

\(\displaystyle \csc{x}\)

\(\displaystyle \sin x\)

\(\displaystyle \cot{x}\)

\(\displaystyle \sec{x}\)

\(\displaystyle \cos{x}\)

Correct answer:

\(\displaystyle \sec{x}\)

Explanation:

 \(\displaystyle \sec{x}=\frac{\text{hypotenuse}}{\text{adjacent}}\), as it is the inverse of the \(\displaystyle \cos{x}\) function.  This is therefore the answer.

Example Question #2 : Graphing The Sine And Cosine Functions

Trig_id

What is \(\displaystyle \theta\) if \(\displaystyle o=10\) and \(\displaystyle a=8\)?

Possible Answers:

\(\displaystyle 89.60^{\circ}\)

\(\displaystyle 55.14^{\circ}\)

\(\displaystyle 51.34^{\circ}\)

\(\displaystyle 53.14^{\circ}\)

\(\displaystyle 0.90^{\circ}\)

Correct answer:

\(\displaystyle 51.34^{\circ}\)

Explanation:

In order to find \(\displaystyle \theta\) we need to utilize the given information in the problem.  We are given the opposite and adjacent sides.  We can then, by definition, find the \(\displaystyle \tan\) of \(\displaystyle \theta\) and its measure in degrees by utilizing the \(\displaystyle \arctan\) function.

\(\displaystyle \tan=\frac{opposite}{adjacent}\)

\(\displaystyle \tan=\frac{10}{8}\)

\(\displaystyle \tan=1.25\)

Now to find the measure of the angle using the \(\displaystyle \arctan\) function.

\(\displaystyle \theta=\arctan1.25\)

\(\displaystyle \rightarrow 51.34^{\circ}\)

If you calculated the angle's measure to be \(\displaystyle 0.90^{\circ}}\) then your calculator was set to radians and needs to be set on degrees.

Example Question #1 : Understanding Arcsine, Arccosine, And Arctangent

\(\displaystyle \sin(x^\circ)=\frac{1}{2}\)

What is \(\displaystyle x\)?

Possible Answers:

\(\displaystyle 30^\circ\)

\(\displaystyle 1^\circ\)

\(\displaystyle 26.57^\circ\)

\(\displaystyle 60^\circ\)

\(\displaystyle 0.009^\circ\)

Correct answer:

\(\displaystyle 30^\circ\)

Explanation:

To get rid of \(\displaystyle \sin(x^\circ)\), we take the \(\displaystyle \arcsin\) or \(\displaystyle \sin^{-1}\) of both sides.

\(\displaystyle \sin(x^\circ)=\frac{1}{2}\)

\(\displaystyle \sin^{-1}(\sin(x^\circ))=\sin^{-1}(\frac{1}{2})\)

\(\displaystyle x^\circ=\sin^{-1}(\frac{1}{2})\)

\(\displaystyle x^\circ=30^\circ\)

Example Question #1 : Understanding Arcsine, Arccosine, And Arctangent

Trig_id

\(\displaystyle o=7.6, h=15.7, \Theta = ?\)

 

Possible Answers:

\(\displaystyle 50.53^{\circ}\)

\(\displaystyle 85.92^{\circ}\)

\(\displaystyle 28.95^{\circ}\)

\(\displaystyle 59.28^{\circ}\)

\(\displaystyle 0.50^{\circ}\)

Correct answer:

\(\displaystyle 28.95^{\circ}\)

Explanation:

In order to find \(\displaystyle \theta\) we need to utilize the given information in the problem.  We are given the opposite and hypotenuse sides.  We can then, by definition, find the \(\displaystyle \sin\) of \(\displaystyle \theta\) and its measure in degrees by utilizing the \(\displaystyle \arcsin\) function.

\(\displaystyle \sin=\frac{opposite}{hypotenuse}\)

\(\displaystyle \sin=\frac{7.6}{15.7}\)

\(\displaystyle \sin=0.4841\)

Now to find the measure of the angle using the \(\displaystyle \arcsin\) function.

\(\displaystyle \theta=\arcsin0.4841\)

\(\displaystyle \rightarrow 28.95^{\circ}\)

If you calculated the angle's measure to be \(\displaystyle \dpi{100} 0.50^{\circ}}\) then your calculator was set to radians and needs to be set on degrees.

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