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GMAT > Math > Geometry > Angle & Triangles

GMAT Math Angle & Triangle Overview

GMAT CAT Line and Angle

The building blocks for geometric forms are lines and angles, so we start by defining these fundamental elements. Although the definitions aren't directly tested, understanding the meanings of these terms is an important part of solving problems on the GMAT. Here are the common terms that pop up on the test:

Line: A straight path of points that extends forever in two directions. A line does not have any width or thickness.
Line segment: The set of points on a line between any two points on the line. Basically it's just a piece of a line from one point to another that contains those points and all the points between.
Bisect: To cut something exactly in half, such as when a line segment cuts another line segment or an angle or a polygon into two equal parts.
Intersect: It simply means to cross; that is, when one line or line segment crosses another line or line segment.
Parallel: Lines that run in the same direction, always remaining the same distance apart. Parallel lines never cross one another.
Angle: The intersection of two rays (or line segments) sharing a common endpoint. The common endpoint is called the vertex .An angle is usually measured in degrees or radians.
Acute angle: Any angle measuring less than 90°.
Right, or perpendicular, angle: An angle measuring exactly 90°.
Obtuse angle: An angle that measures more than 90° but less than 180°.
Straight angle: An angle that measures exactly 180°. A straight angle appears to be a straight line or line segment.
Complementary angles: Angles that add together to total 90°.
Supplementary angles: Angles that add together to total 180°.

GMAT CAT Triangle

A triangle has three sides, and the point where two of the sides intersect is called a vertex. We name triangles by their vertices, so a triangle with vertices A, B, and C is called ΔABC. GMAT usually asks questions on isosceles, equilateral and right triangles.

An isosceles triangle has two equal sides, and the measures of the angles opposite those two sides are also equal to each other. An equilateral triangle has three sides of equal lengths and three angles of equal measure. A right triangle has one angle that measures 90°. The side opposite the right angle is called the hypotenuse.

The GMAT will probably ask you to determine the area of a triangle, so you better be ready. Memorize this formula:

A = ½bh

A stands for (what else) area, b is the length of the base or bottom of the triangle, and h stands for the height (or altitude), which is the distance that a perpendicular line runs from the base to the angle opposite the base.