How to Find the Exact Values of Cosine and Sine of Compound Angles

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SUMMARY

The discussion focuses on finding the exact values of cosine and sine for angles x and y, given that sin x = 3/5 and cos y = 5/13. To determine cos x, the Pythagorean identity sin² x + cos² x = 1 is applied, leading to cos x = 4/5. For sin y, the same identity is utilized, resulting in sin y = 12/13. These calculations are essential for solving problems involving compound angles.

PREREQUISITES
  • Understanding of the Pythagorean identity: sin² θ + cos² θ = 1
  • Knowledge of basic trigonometric functions: sine and cosine
  • Familiarity with angles in the first quadrant
  • Ability to manipulate fractions and perform basic algebra
NEXT STEPS
  • Study the derivation and applications of the Pythagorean identity in trigonometry
  • Learn about compound angle formulas for sine and cosine
  • Explore the unit circle and its relationship to trigonometric functions
  • Practice solving trigonometric equations involving sine and cosine
USEFUL FOR

Students studying trigonometry, educators teaching trigonometric identities, and anyone needing to solve problems involving compound angles.

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Homework Statement



Angles x and y are located in the first quadrant such that sin x = 3/5 and cos y = 5/13.

a) Determine the exact value for cosx
b) Determine the exact value for siny


Homework Equations





The Attempt at a Solution



I don't know what to do.
Am I supposed to do something with the angle a+b?
 
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Use the expression sin2x + cos2x = 1, x being either alpha or beta :) .
 
oh jeez i feel dumb
 

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