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4-7 Simplifying expressions with related angles

4-7 Simplifying expressions with related angles

Point 7 of 11 — Unit 4: Trigonometry — Directed Angles, Functions, Related Angles and GraphsQuestion bank: 0 questions (0 with pictures)

07 4-7 Simplifying expressions with related angles

  • Reduce every term to the same acute angle first, then collect like terms.
  • Example: [sin(180+θ) · cos(360−θ)] / [tan(90+θ) · cos(90−θ)] = [(−sinθ)(cosθ)] / [(−cotθ)(sinθ)] = (−sinθ cosθ)/(−cosθ) = sinθ.
  • For proving identities, transform the harder side only, one valid step at a time, and never "assume the result then work backwards" without reversing the steps.
  • Powers are written sin²θ = (sinθ)²; note that sin²θ + sin²(90−θ) = sin²θ + cos²θ = 1 — a frequent one-mark item.

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