TRIGONOMETRY 1A

Given that Sin Ө  = 1/9, Find Cos Ө.

Solution

Sin²Ө + Cos²Ө = 1

(1/9)² + Cos²Ө = 1

Cos²Ө = 1 - (1/9)²

Cos²Ө = 1 - ¹/81

Cos²Ө =⁸¹/81 - ¹/81

Cos²Ө = ⁸⁰/81

√Cos²Ө = √(⁸⁰/81)       keeping under radical sign both sides

CosӨ =  √(⁸⁰/81)

CosӨ =  √80      since √81=9

                9

CosӨ =  √(2x2x2x5)     

                9

CosӨ =  2√(10)     

                9

CosӨ =  2√10      answer

                 9

  

TRY THIS………

Given that Sin Ө  = 1/5, Find Cos Ө.