1st semester test Flashcards
30-60-90 triangle
A right triangle with interior angle measures of 30°, 60°, and 90°. In a 30-60-90 triangle, the hypotenuse is always twice as long as the shorter leg and the longer leg is √3 times as long as the shorter leg.
45-45-90 triangle
An isosceles right triangle with interior angle measures of 45°, 45°, and 90°. In a 45-45-90 triangle, the two legs have the same length and the hypotenuse is √2 times as long as either leg.
AA similarity postulate
A postulate stating that if two angles of one triangle are congruent to two angles of a second triangle, then the triangles are similar. AA stands for “angle-angle.”
AAS theorem
A theorem stating that if two angles and a nonincluded side of one triangle are congruent to the corresponding two angles and side of another, then the triangles are congruent. AAS stands for “angle-angle-side.”
acute angle
An angle that measures less than 90°. An acute angle is smaller than a right angle.
acute triangle
A triangle in which all three interior angles are acute.
adjacent
Next to each other. Two sides or two angles of a figure are adjacent if they are next to each other.
adjacent angles
Angles that share a vertex and one side.
alternate interior angles
Two angles formed by a line (called a transversal) that intersects two parallel lines. The angles are on opposite sides of the transversal and inside the parallel lines.
altitude of a triangle
The line segment from a vertex of a triangle that is perpendicular to the opposite side or to the line containing the opposite side.
angle
The object formed by two rays that share the same endpoint.
angle addition postulate
If point C lies in the interior of AVB, then mAVC + mCVB = mAVB.
angle bisector
A ray that divides an angle into two angles of equal measure.
angle of incidence
The angle between a ray of light meeting a surface and the line perpendicular to the surface at the point of contact.
angle of reflection
The angle between a ray of light reflecting off a surface and the line perpendicular to the surface at the point of contact.
angles
The corner-like spaces where the sides of a triangle meet.
arc
A part of the circumference of a circle. The symbol means “the arc with endpoints A and B.”
arc length
The length of an arc of a circle.
area
The space taken up by a two-dimensional figure or surface. Area is measured in square units, such as square inches, square centimeters, or square feet.
ASA
An acronym for “angle-side-angle.” These types of problems give you the measure of two angles in a triangle and the length of the side between those two angles. They can be solved using the law of sines.
ASA postulate
A postulate stating that if two angles and the included side of one triangle are congruent to two angles and the included side of another triangle, then the triangles are congruent. ASA stands for “angle-side-angle.”
base
The side of the triangle that is perpendicular to the altitude.
base angles
The two angles formed by the base of a trapezoid and the two adjacent sides.
bases
The parallel sides of a trapezoid.
bisect
To divide into two equal parts.
center of dilation
The point from which a figure is scaled up or down in a dilation.