ISEE Upper Level Math : Plane Geometry

Study concepts, example questions & explanations for ISEE Upper Level Math

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Example Questions

Example Question #5 : Lines

A line  intersects parallel lines  and  and  are corresponding angles;  and  are same side interior angles.

Evaluate .

Possible Answers:

Correct answer:

Explanation:

When a transversal such as  crosses two parallel lines, two corresponding angles - angles in the same relative position to their respective lines - are congruent. Therefore, 

Two same-side interior angles are supplementary - that is, their angle measures total 180 - so

We can solve this system by the substitution method as follows:

Backsolve:

, which is the correct response.

Example Question #1 : How To Find An Angle

Vertical_angles

Note: Figure NOT drawn to scale.

Refer to the above diagram. Give the measure of .

Possible Answers:

Correct answer:

Explanation:

The top and bottom angles, being vertical angles - angles which share a vertex and whose union is a pair of lines - have the same measure, so 

or, simplified,

The right and bottom angles form a linear pair, so their degree measures total 180. That is, 

Substitute  for :

The left and right angles, being vertical angles, have the same measure, so, since the right angle measures , this is also the measure of the left angle, .

Example Question #41 : Plane Geometry

Thingy

Figure NOT drawn to scale

The above figure shows Trapezoid , with  and  tangent to the circle. ; evaluate .

Possible Answers:

Correct answer:

Explanation:

By the Same-Side Interior Angle Theorem, since  and  are supplementary - that is, their degree measures total . Therefore, 

 is an inscribed angle, so the arc it intercepts, , has twice its degree measure;

.

The corresponding major arc, , has as its measure 

The measure of an angle formed by two tangents to a circle is equal to half the difference of those of its intercepted arcs:

Again, by the Same-Side Interior Angles Theorem,  and  are supplementary, so

Example Question #1 : Acute / Obtuse Isosceles Triangles

Two sides of an isosceles triangle have lengths 3 feet and 4 feet. Which of the following could be the length of the third side?

Possible Answers:

Correct answer:

Explanation:

An isosceles triangle, by definition, has two sides of equal length. Having the third side measure either 3 feet or 4 feet would make the triangle meet this criterion.

3 feet is equal to  inches, and 4 feet is equal to  inches. We choose 36 inches, since that, but not 48 inches, is a choice.

Example Question #2 : Acute / Obtuse Isosceles Triangles

The triangles are similar. Solve for .

Question_12

Possible Answers:

Correct answer:

Explanation:

Because the triangles are similar, proportions can be used to solve for the length of the side:

Cross-multiply:

Example Question #661 : Grade 7

One of the base angles of an isosceles triangle is . Give the measure of the vertex angle.

Possible Answers:

Correct answer:

Explanation:

The base angles of an isosceles triangle are always equal. Therefore both base angles are .

Let the measure of the third angle. Since the sum of the angles of a triangle is , we can solve accordingly:

Example Question #1 : How To Find The Length Of The Side Of A Right Triangle

A right triangle has a hypotenuse of 10 and a side of 6. What is the missing side?

Possible Answers:

Correct answer:

Explanation:

To find the missing side, use the Pythagorean Theorem . Plug in (remember c is always the hypotenuse!) so that . Simplify and you get Subtract 36 from both sides so that you get Take the square root of both sides. B is 8.

Example Question #2 : How To Find The Length Of The Side Of A Right Triangle

Right_triangle

Refer to the above diagram. Which of the following quadratic equations would yield the value of  as a solution?

Possible Answers:

Correct answer:

Explanation:

By the Pythagorean Theorem,

Example Question #3 : How To Find The Length Of The Side Of A Right Triangle

Right_triangle

Note: Figure NOT drawn to scale.

Refer to the above diagram. Which of the following quadratic equations would yield the value of  as a solution?

Possible Answers:

Correct answer:

Explanation:

By the Pythagorean Theorem,

Example Question #4 : How To Find The Length Of The Side Of A Right Triangle

Right_triangle

Note: Figure NOT drawn to scale.

Refer to the above diagram.

Find the length of .

Possible Answers:

Correct answer:

Explanation:

First, find .

Since  is an altitude of right  to its hypotenuse, 

 by the Angle-Angle Postulate, so 

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