SAT II Math I : 2-Dimensional Geometry

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

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Example Questions

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Example Question #3 : Analyzing Figures

What is the maximum number of distinct regions that can be created with 4 intersecting circles on a plane?

Possible Answers:

Correct answer:

Explanation:

Try sketching it out.

Q3b

Start with one circle and then keep adding circles like a venn diagram and start counting. A region is any portion of the figure that can be defined and has a boundary with another portion. Don't forget that the exterior (labeled 14) is a region that does not have exterior boundaries.

 

 

Example Question #1 : Analyzing Figures

Q5

Note: Figure may not be drawn to scale

In rectangle  has length and width  and  respectively. Point  lies on line segment  and point  lies on line segment .  Triangle  has area , in terms of  and  what is the possible range of values for ?

Possible Answers:

cannot be determined

Correct answer:

Explanation:

Notice that the figure may not be to scale, and points  and  could lie anywhere on line segments  and  respectively.

Next, recall the formula for the area of a triangle:

To find the minimum area we need the smallest possible values for  and .

To make  smaller we can shift points  and  all the way to point . This will make triangle  have a height of :

 is the minimum possible value for the area.

To find the maximum value we need the largest possible values for  and . If we shift point  all the way to point  then the base of the triangle is  and the height is , which we can plug into the formula for the area of a triangle:

which is the maximum possible area of triangle 

Example Question #1 : Other 2 Dimensional Geometry

Which of the following describes a triangle with sides of length 10 inches, 1 foot, and 2 feet?

Possible Answers:

This is an acute triangle.

This is an obtuse triangle.

This is a right triangle.

More information is needed to answer this question.

This triangle cannot exist.

Correct answer:

This triangle cannot exist.

Explanation:

One foot is equal to 12 inches, so the triangle would have sides 10, 12, and 24 inches. Since 

,

the triangle violates the Triangle Inequality, which states that the sum of the lengths of the two smaller sides must exceed the length of the third. The triangle cannot exist.

Example Question #2 : Other 2 Dimensional Geometry

Which of the following describes a triangle with sides of length nine yards, thirty feet, and 360 inches?

Possible Answers:

The triangle is acute and scalene.

The triangle is acute and isosceles.

The triangle is obtuse and scalene.

The triangle is obtuse and isosceles.

The triangle cannot exist.

Correct answer:

The triangle is acute and isosceles.

Explanation:

Nine yards is equal to  inches.

30 feet is equal to  inches.

In terms of inches, the triangle has sides of length 324, 360, 360; this exists since

and this is an isosceles triangle, since two sides have the same length.

Also,

,

making the triangle acute.

Example Question #3 : Other 2 Dimensional Geometry

Thingy_5

Refer to the above diagram. Which of the following choices gives a set of collinear points?

Possible Answers:

Correct answer:

Explanation:

Collinear points are points that are contained in the same line. Of the four choices, only  fit the description, since all are on Line .

Example Question #4 : Other 2 Dimensional Geometry

You are given triangles   and , with . Which of these statements, along with what you are given, is enough to prove that ?

Possible Answers:

None of the other responses is correct.

 and  have the same perimeter.

Correct answer:

Explanation:

 gives us the congruence of two corresponding angles and one corresponding side;  this is not enough to establish similarity.

The perimeters of the triangles are irrelevant to their similarity, so  and  having the same perimeter does not help to establish similarity, with or without what is given.

 establishes the proportionality of two nonincluded sides of the angles known to be congruent. However, there is no statement that establishes similarity as a result of this.

, along with , sets up the conditions of the Angle-Angle Similarity Postulate, which states that if two triangles have two pairs of congruent angles between them, the triangles are similar.  is the correct choice.

Example Question #71 : Geometry

Regular Octagon  has perimeter 80.  has  as its midpoint; segment  is drawn. To the nearest tenth, give the length of .

Possible Answers:

Correct answer:

Explanation:

Below is the regular Octagon , with the referenced midpoint  and segment . Note that perpendiculars have also been constructed from  and  to meet  at  and , respectively.

Octagon 2

 is a right triangle with legs  and  and hypotenuse .

The perimeter of the regular octagon is 80, so the length of each side is one-eighth of 80, or 10. Consequently,

To find the length of , we can break it down as

Quadrilateral  is a rectangle, so .

 is a 45-45-90 triangle with leg  and hypotenuse ; by the 45-45-90 Triangle Theorem, 

For similar reasons, .

Therefore,

 can now be evaluated using the Pythagorean Theorem:

Substituting and evaluating:

,

the correct choice.

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