Basic Geometry : How to find an angle of a line

Study concepts, example questions & explanations for Basic Geometry

varsity tutors app store varsity tutors android store

Example Questions

Example Question #31 : How To Find An Angle Of A Line

An scalene triangle has has interior angles of , and . How many obtuse interior angles does the triangle have?

Possible Answers:

There is not enough information given. 

Correct answer:

Explanation:

In order to answer the question, we have to figure out what each of the angles is, and then see if any of them are obtuse. The way we do this is to solve for the value of .

To solve for , we must know that the interior angles of a triangle add up to equal .

Therefore, we can set up the following equation and solve for :

We can then plug in this value to find the three angles:

Because an obtuse angle is larger than , none of the angles of this triangle are obtuse. 

Example Question #32 : How To Find An Angle Of A Line

An obtuse angle is an angle that:

Possible Answers:

is equal to 180 degrees

is equal to 90 degrees

is between 0 and 90 degrees

is between 90 and 180 degrees

is between 0 and 45 degrees

Correct answer:

is between 90 and 180 degrees

Explanation:

The definition of an obtuse angle is an angle that ranges between 90 and 180 degrees.

Example Question #31 : How To Find An Angle Of A Line

Find the angle

In the triangle given, find the missing angle. (Triangles are not drawn to scale.)

Possible Answers:

Correct answer:

Explanation:

To find X, we must first find the other two angles that are inside the triangle with the angle X.

The other acute angle is obtainable because we know it is part of a 90 degree angle, with a line at 60 degrees splitting it, leaving it with 30 degrees for that angle. 

Problem 2 geometry

So now that we have one, we need to find the other attainable angle inside the triangle with X in it. The central angles will all equal 360 degrees. We know that one of the angles is 150 degrees, but we are not given the other two. The angle where the right arrow is pointing is attainable because we know the other two angles inside that triangle. 180 degrees minus 30 degrees minus 60 degrees leaves us with 90 degrees. Now, after subtracting 360 degrees from the two angles in the interior (150 degrees and 90 degrees), we find that the missing angle is 120 degrees

  Problem 2 geometry pt 2

Now that we have the two angles needed to find x, the last step is to actually find x.

180 degrees minus 30 degrees minus 120 degrees equals 30 degrees. 

X=30 degrees

Example Question #32 : How To Find An Angle Of A Line

What angle does the line  create with the y-axis? 

Possible Answers:

Correct answer:

Explanation:

The line intersects the y-axis at y = 3. The slope of the line is 2, which means that from y = 3 the next point on the graph is up 2 and over 1. This creates a tiny triangle with the side length adjacent to the angle, on the y-axis, has length 2, and the side length opposite the angle, connecting the y-axis to the graph, has length 1. To find the angle, use tangent: 

Example Question #35 : How To Find An Angle Of A Line

What is the measure of the angle formed by the x-axis and the line  ? 

Possible Answers:

Correct answer:

Explanation:

The slope of the line is 2, so from the point the graph intersects the x-axis, the graph goes up 2 over 1. Just focusing on the point on the x-axis and the point 2 up and 1 to the right creates a small triangle. The side length adjacent to the angle we're looking for, on the x-axis, is 1, and the side length opposite the angle we're looking for, connecting the graph to the x-axis, has length 2. Use tangent to solve: 

Example Question #36 : How To Find An Angle Of A Line

Lines

Refer to the above diagram. 

True or false:  can also be called .

Possible Answers:

False

True

Correct answer:

True

Explanation:

 is defined to be the union of rays  and , the rays that have endpoint  and pass through, respectively,  and . In the diagram below, the two rays - and, consequently, the angle - are indicated in red.

Lines 1

 

 and  also pass through, respectively,  and , and can be called  and . This makes  a valid name for the angle.

Example Question #33 : How To Find An Angle Of A Line

Lines

Refer to the above diagram. 

True or false:  can also be called .

Possible Answers:

False

True

Correct answer:

False

Explanation:

If an angle is named with three letters, the middle letter is always the vertex of the angle. Therefore,  has its vertex at Point , and any three-letter name for this angle must have  as its middle letter. Therefore,  cannot be a valid alternative name for the angle.

Example Question #34 : How To Find An Angle Of A Line

Lines 2

Refer to the above diagram.

True or false:  and  comprise a pair of vertical angles.

Possible Answers:

True

False

Correct answer:

True

Explanation:

By definition, two angles comprise a pair of vertical angles if 

(1) they have the same vertex; and

(2) the union of the two angles is exactly a pair of intersecting lines.

In the figure below,  and  are marked in green and red, respectively:

Lines 2

The two angles have the same vertex, and their union is a pair of intersecting lines. Therefore, the two angles are indeed a vertical pair.

Example Question #691 : Sat Mathematics

Lines 2

Refer to the above diagram.

True or false:  and  comprise a pair of vertical angles.

Possible Answers:

True

False

Correct answer:

False

Explanation:

By definition, two angles comprise a pair of vertical angles if 

(1) they have the same vertex; and

(2) the union of the two angles is exactly a pair of intersecting lines.

In the figure below,  and  are marked in green and red, respectively:

Lines 2

 

While the two angles have the same vertex, their union is not a pair of intersecting lines. The two angles are not a vertical pair.

Example Question #35 : How To Find An Angle Of A Line

Lines 2

Refer to the above diagram.

True or false:  and  comprise a pair of vertical angles.

Possible Answers:

False

True

Correct answer:

False

Explanation:

By definition, two angles comprise a pair of vertical angles if 

(1) they have the same vertex; and

(2) the union of the two angles is exactly a pair of intersecting lines.

In the figure below,  and  are marked in green and red, respectively:

Lines 2

While the two angles have the same vertex, their union is not a pair of intersecting lines. The two angles are not a vertical pair.

Learning Tools by Varsity Tutors