13.1 Distance Formula and circles too‌ Obj: Calculate distances between points and graph circles.
Sketch the following points… • A (-2, 2) • B (-2, -1) • C ( 3, -1) • Next, find the distance between: – Points A and B – Points B and C – Points A and C 01/02/13
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The Distance Formula • The distance d between two points is: (See board)
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Example • Without graphing, find the distance between (-4, 2) and (2, 1).
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Equation of a Circle • For any circle with center (a, b) and radius r.
• (x – a)² + (y – b) ² = r²
(a,b) r
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Example 2 • Find an equation of a circle with center (5, 6) and radius 4. • What do the points on a circle represent?
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Example 3 • Find the equation of a circle with: • A) center (4, -3) and radius 5. • B) center (-1, -2) and radius √3.
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Example 4 • Find the center and radius of each circle. • A) (x – 8)² + (y – 1)² = 64 • B) (x + 9)² + (y – 7)² = 25
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Homework… • Worksheet 13.1 • Skip 11, 12 and 21
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