Lesson Category: Grade 12 Lessons

Notes for lesson 18

Full explanation on this topic and how to answer questions in an exam.

Notes for Inventory valuation.

2. Prove (accepting results established in earlier grades):
   • That a line drawn parallel to one side of a triangle divides the other two
   sides proportionally (and the Midpoint Theorem as a special case of the converse of this theorem);
   • That equiangular triangles are similar;
   • That triangles with sides in proportion are similar; and the Pythagorean
   Theorem by similar triangles

1. Revise the following including grade 10 concepts:
   • The equation of a line through two given points;
   • The equation of a line through one point and parallel or perpendicular to
   a given line; and
   • The inclination (θ) of a line, where 𝑚 = tan 𝜃 is the gradient of the line (0° ≤ 𝜃 ≤ 180°)

2. Apply the equation

that defines a circle with radius r and centre (a ; b)

3.Determine the equation of a tangent to a given circle.