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Master Tangent Properties in Circles: Key Theorems & Applications

Geometry: Master Shapes, Proofs & Spatial Reasoning

Angles and Lines

Angle relationships

Pairs of lines and angles

Parallel lines and transversals

Parallel line proofs

Perpendicular line proofs

Parallel and perpendicular line segments

Identifying Parallel Lines

Identifying Perpendicular Lines

Perpendicular bisectors

Angle bisectors

Angle Bisectors

Coordinate Plane

Cartesian plane

Cartesian Plane — Coordinates

Draw on coordinate planes

Triangles

Pythagorean theorem

Pythagorean Theorem

Using the pythagorean relationship

Applications of pythagorean theorem

Classifying Triangles

Isosceles and Equilateral Triangles

Circles

Angles in a circle

Chord properties 

Tangent properties

Circles and circumference 

Circle properties

Arcs of a circle

Areas and sectors of circles

Central angles and proofs

Inscribed angles and proofs

Central and inscribed angles in circles

Circle chord, tangent, and inscribed angles proofs

Surface Area and Volume

Volume of rectangular prisms word problems

Surface area of 3-dimensional shapes

Introduction to surface area of 3-dimensional shapes

Nets of 3-dimensional shapes

Surface area of prisms

Surface Area of Prisms Rectangle

Calculate the Surface Area

Introduction to volume

Calculate the Volume

Volume of prisms

Find the volume

Volume of Prisms Calculate Area and Volume

Rectangular Prisms Table

Volume of Prisms — Word Problem

Volume of cylinders

Word problems relating volume of prisms and cylinders

Surface area of cylinders

Surface area and volume of prisms

Surface area and volume of pyramids

Surface area and volume of cylinders

Surface area and volume of cones

Surface area and volume of spheres

Transformations

Identifying vertices

Line symmetry

Rotational symmetry and transformations

Understanding tessellations

understand tessellations Interior Angle

Tessellations using translations and reflections

tessellations using translations and reflections

Tessellations using rotations

Introduction to transformations

Horizontal and vertical distances

Similarity

Similar solids

Enlargements and reductions with scale factors

Scale diagrams

Similar triangles

Similar polygons

Congruence

Congruence and congruent triangles

Triangles congruent by SSS proofs

Triangles congruent by SAS and HL proofs

Triangles congruent by ASA and AAS proofs

Logic

Inductive reasoning

Statements

Negations

Conjunctions and disjunctions

Truth tables

Conditionals

Inverses, converses, and contrapositives

Biconditionals

Deductive reasoning

Algebraic proofs

Reasoning

Consecutive integers

Number sequences

Finding the missing digit

math

https://dmn92m25mtw4z.cloudfront.net/img/textbook/textbook-geometry.png

Intro

<p>- Hi, welcome to this question right here. So we're trying to figure out the angle D, C, and the E. So DCE. We're looking for this angle right here, okay? So that angle is missing. So what do we know about the tangent property here? Well, these are the tangent lines. This point right here, this line right here is tangent. Every time you draw a tangent line to your circle, they always form a perpendicular line to the center of your circle. So that will form a 90 degrees for sure because it's perpendicular. So that means this is 90 degrees as well, okay? So what do we have here so far? BDC. This is DC. Actually we don't even need the tangent line because they tell us that there's a triangle right here. There's a triangle right here. Do you see that? The angle here is 100 degrees and these two sides are the same length, represented by the two lines right here and the two lines right there. So what that means is it's an isosceles triangle. So if I just kind of bring that triangle out here, it means that this is 100 degrees and this side and this side is same, that means these two angles here will be identical, okay? So in the triangle, the sum of all the angles are 180, right? If you take away that 100 right right now, you get 80 degrees left over, and that 80 degrees is shared equally between these two angles because this is an isosceles triangle, right?<br />
So divide that by two, you get yourself a 40 degrees. And guess what? That is the angle that they're looking for. So the angle for this question, for the DCE is just 40 degrees, all right? Thanks for watching.</p>


A tangent to a circle must form a perpendicular line from the point of tangency to the center of the circle. In this lesson, we will learn how to use this property, along with others such as, chord properties, to solve questions.

Tangent properties in circle geometry

Tangent properties in circles

What are tangent lines in circles?