SAT II Math II : SAT Subject Test in Math II

Study concepts, example questions & explanations for SAT II Math II

varsity tutors app store varsity tutors android store

Example Questions

Example Question #4 : Graphing Piecewise And Recusive Functions

Define a function \(\displaystyle g\) as follows:

\(\displaystyle g(x) = \left\{\begin{matrix} \sin \frac{x}{2} -1 &x\le - \pi \\ \cos 2x & -\pi < x \le 0 \\ 1-\tan \frac{x }{2}&0< x < \pi \\ 0 & x\ge \pi \end{matrix}\right.\)

At which of the following values of \(\displaystyle x\) is \(\displaystyle g\) discontinuous?

I) \(\displaystyle x = -\pi\)

II) \(\displaystyle x= 0\)

III) \(\displaystyle x= \pi\)

Possible Answers:

I and II only

II and III only

I and III only

None of I, II, and III

All of I, II, and III

Correct answer:

I and III only

Explanation:

To determine whether \(\displaystyle g\) is continuous at \(\displaystyle x = -\pi\), we examine the definitions of \(\displaystyle g\) on both sides of \(\displaystyle -\pi\), and evaluate both for \(\displaystyle x = -\pi\):

 

\(\displaystyle \sin \frac{x}{2} -1\) evaluated for \(\displaystyle x = -\pi\):

\(\displaystyle \sin \frac{-\pi}{2} -1 = \sin \left (- \frac{ \pi}{2} \right )-1= -1-1= -2\)

\(\displaystyle \cos 2x\) evaluated for \(\displaystyle x = -\pi\):

\(\displaystyle \cos 2(-\pi) = \cos (-2\pi)= 1\)

Since the values do not coincide, \(\displaystyle g\) is discontinuous at \(\displaystyle x = -\pi\).

 

We do the same thing with the other two boundary values 0 and \(\displaystyle \pi\).

 

\(\displaystyle \cos 2x\) evaluated for \(\displaystyle x =0\):

\(\displaystyle \cos 2(0) = \cos 0= 1\)

\(\displaystyle 1-\tan \frac{x }{2}\) evaluated for \(\displaystyle x =0\):

\(\displaystyle 1-\tan \frac{0 }{2} = 1 - \tan 0= 1-0 = 1\)

Since the values coincide, \(\displaystyle g\) is continuous at \(\displaystyle x =0\).

 

\(\displaystyle 1-\tan \frac{\pi }{2}\) turns out to be undefined for \(\displaystyle x = \pi\), (since \(\displaystyle \tan \frac{\pi }{2}\) is undefined), so \(\displaystyle g\) is discontinuous at \(\displaystyle x = \pi\).

 

The correct response is I and III only.

Example Question #5 : Graphing Piecewise And Recusive Functions

Define a function \(\displaystyle g\) as follows:

\(\displaystyle g(x) = \left\{\begin{matrix} x^{2}-2x+7 &x\le -1 \\ 9-x & -1 < x \le 0 \\ x+8 &0< x \le 1 \\ x^{2}+3x+ 6& x> 1 \end{matrix}\right.\)

At which of the following values of \(\displaystyle x\) is the graph of \(\displaystyle g\) discontinuous?

I) \(\displaystyle x = -1\)

II) \(\displaystyle x= 0\)

III) \(\displaystyle x= 1\)

Possible Answers:

None of I, II, and III

All of I, II, and III

I and III only

II and III only

I and II only

Correct answer:

II and III only

Explanation:

To determine whether \(\displaystyle g\) is continuous at \(\displaystyle x = -1\), we examine the definitions of \(\displaystyle g\) on both sides of \(\displaystyle -1\), and evaluate both for \(\displaystyle x = -1\):

 

\(\displaystyle x^{2}-2x+7\) evaluated for \(\displaystyle x = -1\):

\(\displaystyle (-1)^{2}-2(-1)+7= 1+2+7 = 10\)

\(\displaystyle 9-x\) evaluated for \(\displaystyle x = -1\):

\(\displaystyle 9-(-1)= 10\)

Since the values coincide, the graph of  \(\displaystyle g\) is continuous at \(\displaystyle x = -1\).

 

We do the same thing with the other two boundary values 0 and 1:

 

\(\displaystyle 9-x\) evaluated for \(\displaystyle x = 0\):

\(\displaystyle 9-0= 9\)

\(\displaystyle x+8\) evaluated for \(\displaystyle x = 0\):

\(\displaystyle 0+8 = 8\)

Since the values do not coincide, the graph of \(\displaystyle g\) is discontinuous at \(\displaystyle x = 0\).

 

\(\displaystyle x+8\) evaluated for \(\displaystyle x = 1\):

\(\displaystyle 1+8 = 9\)

\(\displaystyle x^{2}+3x+ 6\) evaluate for \(\displaystyle x = 1\):

\(\displaystyle 1^{2}+3\cdot 1+ 6 = 1+ 3 + 6 = 10\)

Since the values do not coincide, the graph of \(\displaystyle g\) is discontinuous at \(\displaystyle x = 1\).

 

II and III only is the correct response.

 

Example Question #2 : Graphing Piecewise And Recusive Functions

Define a function \(\displaystyle g\) as follows:

\(\displaystyle g(x) = \left\{\begin{matrix} \sin \frac{x}{2} -1 &x\le - \pi \\ \cos 2x & -\pi < x \le 0 \\ 1-\tan \frac{x }{2}&0< x < \pi \\ 0 & x\ge \pi \end{matrix}\right.\)

Give the \(\displaystyle y\)-intercept of the graph of the function.

Possible Answers:

\(\displaystyle (0, -2)\)

The graph does not have a \(\displaystyle y\)-intercept.

\(\displaystyle (0, -1)\)

\(\displaystyle (0, 1)\)

\(\displaystyle (0,0)\)

Correct answer:

\(\displaystyle (0, 1)\)

Explanation:

To find the \(\displaystyle y\)-intercept, evaluate \(\displaystyle g(0)\) using the definition of \(\displaystyle g\) on the interval that includes the value 0. Since 

\(\displaystyle g(x)= \cos 2x\)

on the interval  \(\displaystyle (-\pi, 0]\),

evaluate:

\(\displaystyle g(x)= \cos 2 \cdot 0 = \cos 0 = 1\)

The \(\displaystyle y\)-intercept is \(\displaystyle (0, 1)\).

Example Question #1 : Graphing Parametric Functions

Give the period of the graph of the equation

\(\displaystyle f(x) = \frac{4}{7} \cos \left ( \frac{3\pi x}{7} \right )\)

Possible Answers:

\(\displaystyle \frac{4}{7}\)

\(\displaystyle \frac{7}{3}\)

\(\displaystyle \frac{14}{3}\)

\(\displaystyle \frac{8}{7}\)

\(\displaystyle \frac{2}{7}\)

Correct answer:

\(\displaystyle \frac{14}{3}\)

Explanation:

The period of the graph of a cosine function \(\displaystyle f(x)= A \cos Nx\) is \(\displaystyle \frac{2 \pi}{N}\), or \(\displaystyle 2 \pi \div N\)

Since  \(\displaystyle N = \frac{3\pi}{7}\), the period is

\(\displaystyle 2 \pi \div \frac{3\pi}{7} = \frac{2 \pi }{1}\times \frac{7} {3\pi}= \frac{14}{3}\)

Example Question #1 : Geometry

Right_triangle_3

Note: Figure NOT drawn to scale.

Refer to the above diagram. \(\displaystyle AD = 6\)\(\displaystyle DC = 24\), and \(\displaystyle \angle ABC\) and \(\displaystyle \angle ADB\) are right angles. What percent of \(\displaystyle \Delta ABC\) is colored red?

Possible Answers:

\(\displaystyle 16 \frac{2}{3} \%\)

\(\displaystyle 33 \frac{1}{3}\%\)

\(\displaystyle 25 \%\)

\(\displaystyle 20 \%\)

\(\displaystyle 30 \%\)

Correct answer:

\(\displaystyle 20 \%\)

Explanation:

\(\displaystyle BD\), as the length of the altitude corresponding to the hypotenuse, is the geometric mean of the lengths of the parts of the hypotenuse it forms; that is, it is the square root of the product of the two:

\(\displaystyle BD =\sqrt{ \left ( AD\right ) \left ( DC\right )} = \sqrt{6 \cdot 24} = \sqrt{144} = 12\).

The area of \(\displaystyle \Delta ADB\), the shaded region, is half the products of its legs:

\(\displaystyle A= \frac{1}{2} (AD) \times (DB ) =\frac{1}{2} \times 6 \times 12 = 36\)

The area of \(\displaystyle \Delta ABC\) is half the product of its hypoteuse, which we can see as the base, and the length of corresponding altitude  \(\displaystyle \overline{BD}\):

\(\displaystyle A = \frac{1}{2} (AC) (BD) = \frac{1}{2} \cdot 30 \cdot 12 = 180\)

\(\displaystyle \Delta ADB\) comprises

\(\displaystyle \frac{36}{180} \times \100 = 20 \%\)

of \(\displaystyle \Delta ADC\).

Example Question #301 : Sat Subject Test In Math Ii

Garden

Note:  Figure NOT drawn to scale

Refer to the above figure, which shows a square garden (in green) surrounded by a dirt path (in orange). The dirt path is seven feet wide throughout. What is the area of the dirt path in square feet?

Possible Answers:

\(\displaystyle 1,001\textrm{ ft}^{2}\)

\(\displaystyle 1,372\textrm{ ft}^{2}\)

\(\displaystyle 1,050\textrm{ ft}^{2}\)

\(\displaystyle 1,904\textrm{ ft}^{2}\)

\(\displaystyle 2,100\textrm{ ft}^{2}\)

Correct answer:

\(\displaystyle 1,904\textrm{ ft}^{2}\)

Explanation:

The area of the dirt path is the area of the outer square minus that of the inner square.

The outer square has sidelength 75 feet and therefore has area

\(\displaystyle 75 \times 75 = 5,625\) square feet.

The inner square has sidelength \(\displaystyle 75 - 2 \times 7 = 61\) feet and therefore has area 

\(\displaystyle 61 \times 61 = 3,721\) square feet.

Subtract to get the area of the dirt path:

\(\displaystyle 5,625 - 3,721 = 1,904\) square feet.

Example Question #3 : Geometry

Garden

Refer to the above figure, which shows a rectangular garden (in green) surrounded by a dirt path (in orange). The dirt path is six feet wide throughout. Which of the following polynomials gives the area of the garden in square feet?

Possible Answers:

\(\displaystyle 2x^{2} - 144\)

\(\displaystyle 2x ^{2} - 36 x + 144\)

\(\displaystyle 2x ^{2} - 18x + 36\)

\(\displaystyle 2x^{2} - 72\)

\(\displaystyle 2x^{2} - 36\)

Correct answer:

\(\displaystyle 2x ^{2} - 36 x + 144\)

Explanation:

The length of the garden is \(\displaystyle 2 \times 6= 12\) feet less than that of the entire lot, or 

\(\displaystyle L = 2x-12\);

The width of the garden is \(\displaystyle 2 \times 6= 12\) less than that of the entire lot, or 

\(\displaystyle W = x-12\);

The area of the garden is their product:

\(\displaystyle A = LW = (2x-12)(x - 12)\)

\(\displaystyle =2x \cdot x - 2x \cdot 12 - 12 \cdot x + 12 \cdot 12\)

\(\displaystyle = 2x ^{2} - 24x - 12 x + 144\)

\(\displaystyle = 2x ^{2} - 36 x + 144\)

Example Question #1 : Geometry

Decagon

The above figure is a regular decagon. If \(\displaystyle AB = 100\), then to the nearest whole number, what is \(\displaystyle AC\)?

Possible Answers:

\(\displaystyle AC \approx 162\)

\(\displaystyle AC \approx 190\)

\(\displaystyle AC \approx 188\)

\(\displaystyle AC \approx 173\)

\(\displaystyle AC \approx 185\)

Correct answer:

\(\displaystyle AC \approx 190\)

Explanation:

As an interior angle of a regular decagon, \(\displaystyle \angle B\) measures

\(\displaystyle m \angle B = \left [\frac{180(10-2)}{10} \right ] ^{\circ }= 144^{\circ }\).

\(\displaystyle AB = BC = 100\).

\(\displaystyle AC\) can be found using the Law of Cosines:

\(\displaystyle \left ( AC\right )^{2} = \left ( AB\right )^{2}+ \left ( BC\right )^{2} - 2 \left ( AB\right ) \left ( BC\right ) \cos m\angle B\)

\(\displaystyle \left ( AC\right )^{2} = 100^{2}+ 100^{2} - 2 \cdot 100 \cdot 100 \cos 144^{\circ }\)

\(\displaystyle \left ( AC\right )^{2} \approx 10,000 + 10,000 - 20,000 (-0.8090)\)

\(\displaystyle \left ( AC\right )^{2} \approx 20,000 - (-16,180) \approx 36,180\)

\(\displaystyle AC \approx \sqrt{36,180} \approx 190\)

Example Question #1 : Geometry

Circle

The circle in the above diagram has its center at the origin. To the nearest tenth, what is the area of the pink region?

Possible Answers:

\(\displaystyle 110.7\)

\(\displaystyle 46.4\)

\(\displaystyle 124.9\)

\(\displaystyle 32.2\)

\(\displaystyle 189.3\)

Correct answer:

\(\displaystyle 124.9\)

Explanation:

First, it is necessary to determine the radius of the circle. This is the distance between \(\displaystyle (0,0)\) and \(\displaystyle (-8,6)\), so we apply the distance formula:

\(\displaystyle r = \sqrt{(x_{2} - x _{1})^{2}+(y_{2} - y_{1})^{2}}\)

\(\displaystyle r = \sqrt{\left ( -8 -0 \right )^{2} +\left ( 6-0\right )^{2} }=\sqrt{ 8^{2}+6^{2}} = \sqrt{64+36 }= \sqrt{100} = 10\)

Subsequently, the area of the circle is 

\(\displaystyle A = \pi r^{2} = \pi \cdot 10^{2} = 100 \pi\)

Now, we need to find the central angle of the shaded sector. This is found using the relationship

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

\(\displaystyle \tan \theta = \frac{6}{-8} = -0.75\)

Using a calculator, we find that \(\displaystyle \tan^{-1}(-0.75) \approx -36.87^{\circ }\); since we want a degree measure between \(\displaystyle 90^{\circ }\) and \(\displaystyle 180 ^{\circ }\), we adjust by adding \(\displaystyle 180 ^{\circ }\), so

\(\displaystyle \theta \approx \left (-36.87+ 180 \right ) ^{\circ } \approx 143.13^{\circ }\)

The area of the sector is calculated as follows:

\(\displaystyle A \approx \frac{143.13 }{360} \cdot 100 \pi \approx 124.9\)

Example Question #1 : Geometry

You own a mug with a circular bottom. If the distance around the outside of the mug's base is  \(\displaystyle 20 \pi cm\) what is the area of the base?

Possible Answers:

\(\displaystyle 100 cm\)

\(\displaystyle 10 \pi cm^2\)

\(\displaystyle 10 cm\)

\(\displaystyle 100 \pi cm^2\)

Correct answer:

\(\displaystyle 100 \pi cm^2\)

Explanation:

You own a mug with a circular bottom. If the distance around the outside of the mug's base is  \(\displaystyle 20 \pi cm\) what is the area of the base?

Begin by solving for the radius:

\(\displaystyle C=2\pi r\)

\(\displaystyle 20 \pi cm=2\pi r\)

\(\displaystyle r=10cm\)

Next, plug the radius back into the area formula and solve:

\(\displaystyle A_{circle}=\pi r^2\)

\(\displaystyle A_{circle}=\pi (10cm)^2=100 \pi cm^2\)

So our answer is:

\(\displaystyle 100 \pi cm^2\)

Learning Tools by Varsity Tutors