circle Last Updated: October 11, 2005

Circle The set of all co-planar points equidistant from a fixed point (center). radius Jeff Bivin -- LZHS

Circle Equation: (x – h)2 + (y – k)2 = r2 r (h, k) Jeff Bivin -- LZHS

Circle r = r = 11 x – 3 = 0 x = 3 y – 5 = 0 y = 5 121 11 (3, 5) center Jeff Bivin -- LZHS

Circle r = r = 9 x + 5 = 0 x = -5 y – 2 = 0 y = 2 81 9 (-5, 2) center Jeff Bivin -- LZHS

Graph the following circle 9x2 + 36x + 9y2 - 18y - 10 = 89 9x2 + 36x + 9y2 - 18y = 89 + 10 9x2 + 36x + 9y2 - 18y = 99 9 (x2 + 4x + 22 ) + (y2 - 2y + (-1)2 ) = 11 + 4 + 1 (x + 2)2 + (y - 1)2 = 16 Jeff Bivin -- LZHS

Circle r = r = 4 x + 2 = 0 x = -2 y – 1 = 0 y = 1 16 4 (-2, 1) center Jeff Bivin -- LZHS

Graph the following circle 4x2 + 24x + 4y2 + 32y + 13 = 157 4x2 + 24x + 4y2 + 32y = 157 - 13 4x2 + 24x + 4y2 + 32y = 144 4 (x2 + 6x + 32 ) + (y2 + 8y + 42 ) = 36 + 9 + 16 (x + 3)2 + (y + 4)2 = 61 Jeff Bivin -- LZHS

Circle r = x + 3 = 0 x = -3 y + 4 = 0 y = -4 61 61 (-3, -4) center Jeff Bivin -- LZHS

Graph the following circle 5x2 - 80x + 5y2 + 20y - 34 = 106 5x2 - 80x + 5y2 + 20y = 106 + 34 5x2 - 80x + 5y2 + 20y = 140 5 (x2 - 16x + (-8)2 ) + (y2 + 4y + 22 ) = 28 + 64 + 4 (x - 8)2 + (y + 2)2 = 96 Jeff Bivin -- LZHS

Circle r = r = 4 6 x - 8 = 0 x = 8 y + 2 = 0 y = -2 96 4 6 (8, -2) 4 6 y + 2 = 0 (8, -2) y = -2 center (8, -2) Jeff Bivin -- LZHS

Graph the following circle 2x2 + 10x + 2y2 + 8y + 4 = 25 2x2 + 10x + 2y2 + 8y = 25 - 4 2x2 + 10x + 2y2 + 8y = 21 2 (x2 + 5x + ) + (y2 + 4y + 22 ) = + + 4 (x + )2 + (y + 2)2 = Jeff Bivin -- LZHS

Circle r = r = x + = 0 x = y + 2 = 0 y = -2 center Jeff Bivin -- LZHS