Answer:
17.4cm
Step-by-step 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
