Given a triangle with b = 3, c = 9 , and a =21 ° what is the length of a? round to the nearest tenth

Length of a is 6.3

Step-by-step explanation:

Given: b = 3  , c = 9  and ∠A = 21°

To find: value of a.

We use law of cosines.

The law of cosines is used for calculating one side of a triangle when the angle opposite and the other two sides are known.

a² = b² + c² - 2bc × cos A

a² = 3² + 9² - 2 × 3 × 9 × cos(21)

a² = 9 + 81 - 54 × 0.93

a² =  39.78

a = √39.78

a = 6.307

a = 6.3

Therefore, length of a is 6.3

b

step-by-step explanation: