Geometry Flashcards
Diameter
d=2r
Circumference
c/d = π
or
πd = c
or
c = 2πr
Circle Area
A = πr2
Central Angle
A central angle is an angle whose apex is the center O of a circle and whose legs are radii intersecting the circle in two distinct points A and B
Sector Area
Sector Area = Fraction x Entire Area
Arc Length
Arc Length = Fraction x Entire Circumference
Sum of internal angles of a triangle
180º
Triangle
Perimeter
Sum of all 3 sides
Triangle
Area
1/2 bh
How do you find the perimeter of a right triangle?
a2 + b2 = c2
Common triangle triples
Right Triangles
3-4-5
6-8-10
5-12-13
18-24-30
Parallelogram
Area
base x height
The diagonal of a rectangle
semi circle
What is the ratio of a 30-60-90
x : x√3 : 2x
The hypotenuse is 2x
the shortest side (30°) is x
60° Is x√3
A triangle inscribed in a semi circle is
A right triangle
Use Pythagorean theorem
Area of a trapezoid
Slope of a line
Ratio of a 45-45-90
Relationship between sides and angles of a triangle
Sum of the angles of any polygon
In the coordinate plane, a circle has a center of (2,-3) and passes through the point (5,0). What is the area of the circle?
Answer E
A ladder of a fire truck is elevated to an angle of 600 and extended to a length of 70 ft. If the base of the ladder is 7 feet above the ground, how many feet above the ground does the ladder reach?
Relationship between a central angle and the arc it intercepts is
Central angle / 360 x circumference = arc length
Relationship between a an inscribed angle and the arc it intercepts is
Inscribed angle = 1/2 intercepted arc
Surface area of a cylinder
A = 2πrh + 2πr2
Volume of cylinder
πr2h
Central angle of 1/4 circle
90º
Circle
sector area = fraction x entire area
sector area = fraction x entire area
Circle
arc length
Arc length = fraction x entire circumference
Angles of triangle must sum to
180º
Angles of right isosceles
45-45-90 has two equal sides
