gaja118

=CHAPTER 9=

=__SECTION 9.1- CHORDS AND ARCHS__= - a **circle** is the set of all points in a plane that are equidistant from a given point in the plane known as the center of the circle - a **radius** is a segment from the center of the circle to a point on the circle - a **chord** is a segment whose endpoints lie on a circle - the **diameter** is a chord that contains a point in the center of the circle - an **arc** is an unbroken part of a circle - a **semicircle** is an arc whose endpoints are endpoints of a diameter - a **minor arc** is an arc that is less than half of the circle - a **major arc** is an arc that is more than half of a cricle - a **central angle** is an angle in the plane of a cricle whose vertex is the center of the circle - the **intercepted arc** of a central angleis an arc whose endpoints lie on the sides of the angle and whose other points lie in the interior of the angle - the degree measure of a minor arc is the measure of its central angle - the degree measure of a major arc is 360 minus the degree measure of its minor arc - this is the formula to find the arc length on a circle: length= arc degree measure ÷ 360° {2•pie•r}

=__SECTION 9.2- TANGENTS TO CIRCLES__= - a **secant** to a circle is a line that intersects the crcle at 2 points - a **tangent** is a line in the plane of the cricle that meets the cirlce at only 1 point, this point is known as the the point of tangency =__SECTION 9.3- INSCRIBED ANGLES AND ARCS__= - an **inscribed angle** is an angle whose vertex lies on a cirlce and whose sides are chords of the circle, or an angle that is only inside a circle

- the 2 inscribed angle theorems: 1- **Right Angle Corollary:** if an inscribed angle intercepts a semi circle, then the angle is a right angle. 2- **Arc-Intercept Corollary:** if two inscribed angles intercept the same arc, then they have the same measure.

=__SECTION 9.4- ANGLES FORMED BY SECANTS AND TANGENTS__= - there are three ways to classify angle in or around circles: 1: the vertex of the angle lies on the circle 2: the vertex of the angle is inside the circle 3: the vertex of the angle is outside of the cricle

=__SECTION 9.5- SEGMENTS OF TANGENTS, SECANTS, AND CHORDS__= - use the diagram below to identify parts of tangents and secants on a circle, - segment XA is a tangent segment - segment XB is a secant segment - segment XC is an external secant segment - segment BC is a chord

=__SECTION 9.6- CIRCLES IN THE COORDINATE PLANE__= - graphing a circle requires the x and y coordinates to be squared - an example of a circle in a coordinate plane:

=THE END! :- )=