Question

Use cosine law to find the value of x. Show working. use ^ for power and sqrt for square root

Answer 1

x ≈ 11.89

Explanation:

Using the cosine rule

x² = 4² + 9² - ( 2 × 4 × 9 × cos128° )

= 16 + 81 - 72cos128°

= 97 - (- 44.33 )

= 141.33 ( take the square root of both sides )

x =
`√(141.33)` ≈ 11.89 ( to 2 dec. places )

Answer 2

See the picture below