18个圆问题切线弦模块.pdfVIP

Module C1 Module C2 AQA Edexcel MEI/OCR OCR Certain images and/or photos on this presentation are the copyrighted property of JupiterImages and are being used with permission under license. These images and/or photos may not be copied or downloaded without permission from JupiterImages Tangents to Circles Some properties of circles may be needed in solving problems. This is the 1st one ➢ The tangent to a circle is perpendicular to the radius at its point of contact A line which is perpendicular to a tangent to any curve x is called a normal. radius For a circle, the radius is a normal. tangent Tangents to Circles Diagrams are very useful when solving problems involving circles e.g.1 Find the equation of the tangent at the point (5, 7) on a circle with centre (2, 3) Method: The equation of any gradient m straight line is y =mx +c. x We need m , the gradient of gradient m1 (5, 7) the tangent. y 2 -y 1 (2, 3) x Find m1 using m = • The tangent to a x 2 -x 1 perpendicular to he radius tangent at its point of co 1 • Find m using m2 = -