Question

R

SECTION II (50 MARKS)
Answer ANY FIVE questions in this section.
17) In a triangle ABC, BC=8cm, AC=12cm and angle ABC=120
a) Calculate the length of AB, correct to one decimal place (4marks)​

Answer 1

17.4cm

Explanation

17) In a triangle ABC, BC=8cm, AC=12cm and angle ABC=120

To get the length of AB, we will use the cosine rule

AB² = BC² + AC² - 2(BC)(AC) cos <ABC

AB² = 8² + 12² - 2(8)(12) cos 120

AB² = 64 + 144 - 192cos12

AB² = 208 - (-96)

AB² = 208 +96

AB² = 208 - (-96)

AB² = 304

AB² = 17.4cm

Hence the length of AB is 17.4cm