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Fundamental Identity

Core Pythagorean identity

Grade 9 · Fundamental Identity

Easy 20 questions Worksheet #57556 For Fundamental Identity

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MathDigits Worksheet

Grade 9 · Fundamental Identity

Easy · 20 questions · Worksheet #57556 · Fundamental Identity

Name: ________________________

Date: ______________ Score: ______

  1. fill If sin θ = 0.8, find cos θ using sin²θ + cos²θ = 1. (positive value)
    ______________________________
  2. fill If sin θ = 0.5, find cos θ using sin²θ + cos²θ = 1. (positive value)
    ______________________________
  3. fill If sin θ = 0.6, find cos θ using sin²θ + cos²θ = 1. (positive value)
    ______________________________
  4. fill If sin θ = 0.8, find cos θ using sin²θ + cos²θ = 1. (positive value)
    ______________________________
  5. fill If sin θ = 0.8, find cos θ using sin²θ + cos²θ = 1. (positive value)
    ______________________________
  6. fill If sin θ = 0.5, find cos θ using sin²θ + cos²θ = 1. (positive value)
    ______________________________
  7. fill If sin θ = 0.5, find cos θ using sin²θ + cos²θ = 1. (positive value)
    ______________________________
  8. fill If sin θ = 0.6, find cos θ using sin²θ + cos²θ = 1. (positive value)
    ______________________________
  9. fill If sin θ = 0.6, find cos θ using sin²θ + cos²θ = 1. (positive value)
    ______________________________
  10. fill If sin θ = 0.5, find cos θ using sin²θ + cos²θ = 1. (positive value)
    ______________________________
  11. fill If sin θ = 0.5, find cos θ using sin²θ + cos²θ = 1. (positive value)
    ______________________________
  12. fill If sin θ = 0.5, find cos θ using sin²θ + cos²θ = 1. (positive value)
    ______________________________
  13. fill If sin θ = 0.8, find cos θ using sin²θ + cos²θ = 1. (positive value)
    ______________________________
  14. fill If sin θ = 0.5, find cos θ using sin²θ + cos²θ = 1. (positive value)
    ______________________________
  15. fill If sin θ = 0.5, find cos θ using sin²θ + cos²θ = 1. (positive value)
    ______________________________
  16. fill If sin θ = 0.8, find cos θ using sin²θ + cos²θ = 1. (positive value)
    ______________________________
  17. fill If sin θ = 0.6, find cos θ using sin²θ + cos²θ = 1. (positive value)
    ______________________________
  18. fill If sin θ = 0.8, find cos θ using sin²θ + cos²θ = 1. (positive value)
    ______________________________
  19. fill If sin θ = 0.6, find cos θ using sin²θ + cos²θ = 1. (positive value)
    ______________________________
  20. fill If sin θ = 0.8, find cos θ using sin²θ + cos²θ = 1. (positive value)
    ______________________________

Updated July 2026

FAQs

What is Fundamental Identity?

Fundamental Identity (trig identity) is a trigonometry relationship written as Core Pythagorean identity or sin²θ + cos²θ = 1. Students use it to solve unknowns when enough values are known.

How do you calculate Fundamental Identity step by step?

Write Core Pythagorean identity, substitute the known numbers carefully, then simplify. Worked walkthrough: If sin θ = 0.6 cos²θ = 1 − 0.36 = 0.64 cos θ = 0.8.

When is Fundamental Identity taught in school?

Fundamental Identity usually appears in trigonometry units during middle or secondary school. Match difficulty with MathDigits grade worksheets so practice fits the curriculum year.

What is a real example of Fundamental Identity?

On this page the worked result is cos θ = 0.8. Generate a formula worksheet below for more unique practice sets.

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