Line, line segment, segment of a line, what does it all mean? Endpoints, midpoints, names of lines, names of segments. Watch this video and learn the definitions of these terms.

Angles are identified by the measurement of their angles. Well, that would make sense. The instructor illustrates four different angles and their names by identifying their degrees. Zero to less than 90 degrees is an acute angle, while...

Supplementary, obtuse, acute, complementary angles. It's good to know what all of these mean, but let's focus on one at a time. Complementary angles always add up to 90 degrees. So if given one angle in a complementary angle problem, the...

Are complementary angles nice to each other? That's not what complementary means in math. Complementary angles are two angles that add up to 90 degrees and form a right triangle. So if given one value in a problem about complementary...

Understand the difference in finding angle measures. A segment of an extensive geometry playlist introduces the formula to find the measure of an angle formed outside of a circle. Using examples, the video shows how to calculate measures...

Squares, pentagons, triangles, polygons. How is it possible to figure out the sum of the interior angles of any of these multi-faceted shapes? There's got to be a formula. Of course there's a formula. That's what algebra is all about,...

Defining the undefined is the goal of this video. The instructor explains the important features of a point, line, and plane and how they work together. He also addresses the correct ways to name each and describes the correct notation —...

A tangent line always finds its place at a 90-degree angle to a radius. Many scholars struggle with the proof of the seemingly simple statement. A brief video demonstrates the reasoning behind the proof before pupils practice applying it...

Delving into proof that the diagonals of a rhombus are perpendicular to each other, this lecture evaluates the angles and sides of this figure. It would serve as a great test preparation activity.

Skew lines? What? By definition, skew lines are lines on different planes that never intersect. Watch this video and get an explanation along with a visual diagram.

Eight is the lucky number of angles when a line crosses two parallel lines. Scholars watch a concise video in the Socratica Geometry series to learn about angles made by parallel lines and a transversal. Using corresponding and vertical...

What are supplementary angles? They are two angles that when added together make 180 degrees on a straight angle line. Hard to picture that? Then watch this video and see how the instructor illustrates this on a diagram.

An angle is formed when two rays share a common endpoint. Want to know more about angles? There are a lot of terms in this lesson. You might have to watch it two or even three times to make sure you understand all the terms. I recommend...

What are the exterior angles of a polygon? Polygons have exterior angles? How? Oh, extend all the lines, and find the value of each of the supplementary angles. No problem as long as one knows what supplementary angles means. Not sure?...

The interior angles of any and ALL triangles adds up to 180 degrees. So if given two of the angle degrees, is it possible to find the value of the third angle? Yes! Use the triangle sum theorem to solve for the missing angle. Watch this...

Triangles bring sums to geometry. The lesson presents two theorems dealing with the angles of a triangle. Pupils learn about the Triangle Sum Theorem and the Exterior Angle Theorem, and then apply the theorems to create equations and...

What properties of equality also work for congruence? Part of basic geometry playlist, the video relates algebraic properties to their counterparts of congruence. Learners see how the properties mean the same whether with equality or...

Trapezoids can be tricky! Break down the process of finding the area of a trapezoid with an engaging math video. Learners explore area formula and shown exactly how to plug in information, solve, and simplify. 

Face the vertex of two-dimensional shapes and discover what each figure requires as part of its classification. With one shape per slide, learners see what makes each shape special and compare it to others with similar qualities. 

Pupils review the vocabulary, formulas, and postulates from the opening unit in Geometry. Individuals use these to solve a problem set that requires learners to apply algebraic skills along with providing reasons within a proof. Scholars...

Back with "more energy," Sal begins his explanation of problems 15-18 on page 412 of The Official SAT Study Guide. Problems include angles of equilateral triangles, rectangles, and graphing slopes.

Finding perimeters and slopes is the focus of this video, which details ways to solve problems 15-17 on the practice SAT. Even students who are confident in their ability to pass the SAT would benefit from this additional review.

Using the definition of a trapezoid, the segment within a large playlist on basic geometry explains other properties of trapezoids. The video introduces the special properties held by isosceles trapezoids.

The final video of the SAT practice series takes students through increasingly complicated algebra and geometry problems, but Sal works steadily through each mathematical process. At the end of the video he tells students that they are...