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Naming sides and basic ratios

Naming sides and basic ratios

Right-angled triangle relative to angle θ\thetaθ:

          θ
          o
         /|
        / |
       /  | adjacent
      /   |
     /    |
    o-----o
     opposite

Trigonometric ratios link an angle to side lengths. In a right-angled triangle, the side names depend on the chosen angle θ\thetaθ.

With θ\thetaθ at the top vertex and the right angle at the bottom-right corner:

  • the vertical side next to θ\thetaθ is the adjacent side
  • the sloping longest side is the hypotenuse
  • the bottom horizontal side across from θ\thetaθ is the opposite side

Trigonometric Ratios Lesson

  1. A Level
  2. /Maths
  3. /Trigonometric Ratios

Step-by-step lessons on Edexcel A Level Maths Trigonometric Ratios, covering 9.1 The Cosine Rule, 9.2 The Sine Rule, 9.3 Areas of Triangles, 9.4 Solving Triangle Problems, 9.5 Graphs of Sine, Cosine and Tangent, and 9.6 Transforming Trigonometric Graphs. Each one builds up to exam-style questions. Build fluency with the core pure algebra and calculus toolkit early, since almost every mechanics and statistics topic on the course depends on it.

Lessons