GMAT Quant Chapter 17: Geometry Flashcards
Define supplementary angles.
Their angles sum to 180 degrees.
What is the relationship between the size of the sides and the size of the angles in a triangle?
The largest angle is always opposite the longest side of the triangle, the smallest angle is always opposite the shortest side of the triangle.
define an exterior angle
the angle created by one side of the triangle and the extension of an adjacent side
What is the sum of the exterior angles for any polygon?
(taking one exterior angle in a straight line from each vertex)
360 degrees
What fact do we know about the interior and exterior angles of a triangle?
Exterior angle is equal to the sum of the two interior angles it is not connected to
What is the standard formula for the area of a triangle?
Base x Height x 1/2
What inequality is there about the length of a triangle’s sides?
The sum of 2 lengths of any 2 sides of the triangle > length of the third side
Define isosceles triangle
At least 2 sides of the same length, at least two angles are the same
What are the 3 most common Pythagorean Triples?
3-4-5
5-12-13
8-15-17
What is another name for an isosceles right triangle and what are its properties?
45-45-90 triangle
Area = equal length sides ^2 / 2
ratio of the sides = x : x : x Root 2
Area is half of the square
What is the area of an equilateral triangle?
What kind of triangle appears when we cut an equilateral triangle in half?
side ^ 2 Root 3 / 4
2 x 30-60-90 triangles
What are the 3 versions of triangle similarity (scale)?
- 3 angles measure the same for both triangles
- 3 pairs of corresponding sides have lengths in same ratio
- Angle of 1 triangle = angle of another triangle and the sides are in the same ratio
What are laws about the squares and rectangles?
All squares are rectangles
All rectangles are parallelograms
What facts do we know about parallelograms?
opposite sides are equal in length
opposite angles are equal in measure
any 2 consecutive angles are supplementary
What must we remember about the division of a rectangle into two right triangles?
only divide into two 30-60-90 triangles if the ratio of width : length is…
X: X Root 3
or
1 : Root 3
What is the length of the diagonal line between two corners of a square?
side Root 2
What fact do we know about the maximum area of a rectangle?
What fact do we know about the minimum perimeter of a rectangle?
If a square and a rectangle have the same perimeter, the square will always have the greater area.
If the rectangle and square have equal areas, the square will always have the smallest perimeter.
What formula do we use to calculate the area of a trapezoid?
What do you call a trapezoid with two parallel sides of equal length?
Area = (base 1 + base 2) * height / 2
isosceles trapezoid
How can we calculate the sum of the interior angles of any polygon?
How can we calculate the interior angle of a regular polygon?
(n -2) * 180
where n is the number of sides of the polygon
(n-2) * 180 / n
Define “regular” when it is used in the phrase regular polygon.
All sides are the same length and all interior angles are equal