# Geometry Assignment Find The Missing Length Indicated Probability

Easy to use online **geometry calculators and solvers** for various topics in geometry such as calculate area, volume, distance, points of intersection. These may be used to check homework answers, practice or explore with various values for deep understanding.

- Right Triangle Calculator and Solver. Four easy to use calculators to solve right triangle problems depending on which information about the triangle you are given.
- Solve a Triangle Given its Vertices. Calculator to calculate all three angles and three sides of the triangle.
- Perimeter and Area of a Triangle Given its Vertices. Online calculator to calculate the area and perimeter of a triangle given the coordinates of its vertices.
- Heron's Formula for Area of a Triangle. Calculate the area of a triangle using heron's formula and when the three sides of a triangle are known.
- Heron's Formula for Area of a Triangle. An online geometry calculator to calculate the area of a triangle using sine formula when two sides and the angle between them are known (SAS case).
- Area, Perimeter and Diagonal of a Rectangle - Calculator. Calculate the area, perimeter and diagonal of a rectangle given its dimensions (length and width).
- Length and Width of Rectangle - Calculator. Calculate the dimensions (length and width) of a rectangle given the area A and perimeter P of the rectangle.
- Rectangle Area Diagonal Calculator. An online calculator to calculate the length and width (dimensions) of a rectangle given its area and diagonal.
- Rectangle Perimeter Diagonal Calculator. An online calculator to calculate the length and width (dimensions) of a rectangle given its perimeter and diagonal.
- Area and Perimeter of a Square - Geometry Calculator. Online calculator to calculate the area and perimeter of a square given the length of its side.
- Ellipse Area and Perimeter Calculator. An online calculator to calculate the area and perimeter of an ellipse given its semi axes.
- Ellipsoid Volume Calculator. An online calculator to calculate the volume of an ellipsoid given its semi axes.
- Surface Area and Volume of Pyramid - Geometry Calculator. An online calculator to calculate the surface area, the volume and many other parameters of a pyramid given the dimensions of its
**rectangular**base and its height. - Surface Area and Volume of Right Cone - Geometry Calculator. Calculate the surface area and the volume of a right cone given its radius and height.
- Surface Area and Volume of Right Cylinder - Geometry Calculator. Calculate the surface area and the volume of a right cylinder given its radius and height.
- Surface Area and Volume of Frustum - Geometry Calculator. Calculate the surface area, the volume and other parameters of a Frustum given its radius R at the base, its radius r at the top and its height h.
- Volume and Surface Area of a Solid Rectangle. Calculate the volume and the surface area of a solid rectangle given its length, width and height.
- Volume and Surface Area of a Sphere. calculate the volume and the surface area of a sphere given its radius.
- Distance Between two Points in Polar Coordinates - Calculator. A calculator to calculate the distance between two points in polar coordinates. The polar angle may be in degrees or radians.
- Distance and Midpoint in 3D Geometry - Calculator. Online calculator to calculate the distance between two points and their midpoint when these points are given by their cartesian coordinates in a 3 dimensional space
- Area of Triangle Defined by Lines Calculator. An Online calculator to calculate the area of a triangle defined by three lines.
- Collinear Points Calculator. Online calculator to find out whether three given points are collinear or not.
- Concurrent Lines Calculator. Online calculator to find out whether three given lines are concurrent, that is they all pass through the same point.
- Rhombus - Geometry Calculator. Calculator to calculate the characteristics of a rhombus.
- Parallelogram Area Calculator. Calculator to calculate the area of a parallelogram.
- Trapezoid Area Calculator. Calculator to calculate the area of a trapezoid given the bases and the height.
- Trapezoid Calculator and Solver. An easy to use online calculator to solve trapezoid problems. The area, the angles and the diagonals of a Trapezoid are calculated given its 4 sides.
- Area and Perimeter of a Circle - Geometry Calculator. An online calculator to calculate the area and perimeter of a circle given its radius.
- Arc Length and Area of a sector - Geometry Calculator. Calculate the arc length S and area A of a sector given its radius and its central angle t.
- Area of a Circular Ring. Calculate the area of a circular ring when outer and inner radii are known.
- Radius of Inscribed Circle - Geometry Calculator. Calculate the radius of a circle inscribed inside a triangle of sides a, b and c.
- Radius of Circumscribed Circle - Geometry Calculator. Calculate the radius of a circumscribed circle of a triangle of sides a, b and c.
- Regular Polygons Calculator. Online calculators to calculate side, the radius of inscribed circle, the radius of circumscribed circle and area of polygons.
- Irregular Polygon Area Calculator.Online calculator to calculate the area of an irregular polygon whose vertices are given by their Cartesian coordinates.
- Pythagorean Theorem Calculator. Use Pyhthagorean theorem to find side and hypotenuse a right triangle.
- Cosine Law Calculator and Solver. Calculator that solves triangle problems given 3 sides (SSS case) or 2 sides and 1 included angle (SAS case).
- Sine Law Calculator and Solver. Calculator that solves triangle problems given 2 angles and one side (ASA and AAS cases) or 2 sides and one opposite angle (SSA case). The SSA case includes one, two or no solutions.
- Geometry Tutorials and Problems

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## Pythagora Theorem Calculators

## Sine and Cosine laws Calculators

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## Finding Missing Angles

Home > By Subject > Geometry > Finding Angles

The three examples below show how angle relationships and the properties of triangles can be used to find unknown angles. You can review angle properties here.

Work through the examples below with your children. Discuss alternate ways of finding the missing angles as there are often other ways of finding them.

## Finding Angles: Example 1

What are the measures of the angles located at positions a, b, & c? Note: the figure is symmetrical on the vertical through angle b. | |

The large triangle is an isosceles triangle. The two angles on the base are equal. | Angle a = 35° |

We now know two angles in the largest triangle. The third angle, angle b must add to these to make 180°. | 35° + 35° + b = 180° b = 180° - 70° b = 110° |

We now know two angles in a quadrilateral. The two unknown angles, including angle c are equal. All four angles add up to 360°. | 2c + 110° + 120° = 360° 2c = 360° - 230° 2c = 130° c = 65° |

## Finding Angles: Example 2

What are the measures of the angles located at positions a, b, c, d, e, & f? Note: the figure is symmetrical on the vertical through angle f. | |

Looking along the base of the large triangle. Angle a added to 75° and 70° equals 180°. | a + 75° + 70° = 180° a = 180° - 145° Angle a = 35° |

Looking at the small triangle that includes angle b we now know that a = 35° and, since the sum of the triangles equal 180° we can find angle b. | 35° + 95° + b = 180° b = 180° - 130 ° b = 50° |

Angle c and the 95° angle are supplementary; they add up to 180°. | c + 95° = 180° Angle c = 85° |

Now we know c = 85° we can find angle d since the three angles in the triangle add up to 180°. | 85° + 70 ° + d = 180° d = 180° - 155 ° d = 25° |

The triangle in the middle is isosceles so the angles on the base are equal and together with angle f, add up to 180°. | e = 75° 75° + 75° + f = 180° f = 180° - 150° f = 30° |

## Finding Angles: Example 3

What are the measures of the angles located at positions a, b, c, d, e, & f? | |

Angle a and the 70° angle are opposite angles so they are equal. | Angle a = 70° |

Angle b and the 135° angle are supplementary so they add up to 180°. | 135° + b = 180° b = 180° - 135° b = 45° |

We now know two angles in a triangle. These two angles along with angle c add up to 180°. | c + 70° + 45° = 180° c = 180° - 115° c = 65° |

Angles d and b are alternate angles and, since the two lines are parallel, they are equal. | d = 45° |

Angle e and the 70° angle are corresponding angles and, since the two lines are parallel, they are equal. | e = 70° |

Angle f and angle e are supplementary. They add up to 180°. | 70° + f = 180° f = 180° - 70° f = 110° |

In the above examples the discovery of each angle followed on from finding other angles. The missing angles will not always be labeled a, b, c, d, etc. so the sequence in which to find angles might not be obvious. Sometimes it is best to just start finding whatever angles you can and keep going until all the ones that are required are found.

## Missing Angles Worksheets

Print out the worksheets below to help your children practice finding missing angles.

## Reminders

- Sum of the angles in a triangle = 180°
- Sum of the angles in a quadrilateral = 360°
- Opposite angles are equal
- For two parallel lines and a transversal,
- corresponding angles are equal, and
- alternate angles are equal.

Try the 180° In a Triangle Experiment which is a 2-page (be careful with the scissors) activity to demonstrate that the sum of the interior angles in a triangle is 180°

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