TRIGONOMETRY A6

Given that Sin Ө  = 4/9, Find Cos Ө.

Solution

Sin²Ө + Cos²Ө = 1

(6/9)² + Cos²Ө = 1

Cos²Ө = 1 - (6/9)²

Cos²Ө = 1 - ³⁶/81

Cos²Ө =⁸¹/81 - ³⁶/81

Cos²Ө = ⁴⁵/81

CosӨ =  √(⁴⁵/81)

CosӨ =  √45      

                9

CosӨ =  √(9X5)     

                9

CosӨ =  3√5     

                9

CosӨ =  √5      answer

               3

TRY THIS………

Given that Sin Ө  = 5/8, Find Cos Ө.