Mathematics for IGCSE & O level - Pythagoras' Theorem And Trigonometry (Section 5 - No. 4)
If you have a triangle with sides 6cm, 8cm and angle between the two is 60 degrees, what is the length of the third side?
7.84cm
4.0cm
7.21cm
9.24cm
คำอธิบาย
Using the cosine rule, c² = 6² + 8² - 2 * 6 * 8 * cos(60), c = 7.211