The identity sin^2theta + cos^2theta = 1 comes from applying Pythagoras' theorem to:

  1. a circle of radius 2
  2. a square
  3. a right triangle with hypotenuse 1 (a point on the unit circle)
  4. an equilateral triangle
Answer

C) a right triangle with hypotenuse 1 (a point on the unit circle)

With hypotenuse 1, the legs are costheta and sintheta, so cos^2theta + sin^2theta = 1^2. SLO M-09-B-23 · Knowledge

Mathematics MCQ · More Trigonometric Identities MCQs · Practise