Practicing Success
Practicing Success
CUET Preparation Today
In a triangle ABC, if the three sides are a=5, b=7 and c=3, what is angle B? |
120º 60º 90º 150º |
120º |
By using cosine rule :- cos B = \(\frac{ 5² + 3² - 7²}{ 2 × 5 × 3}\) = \(\frac{ 25 + 9 - 49}{ 30}\) = \(\frac{ - 15}{ 30}\) = \(\frac{ - 1}{ 2}\) cosB = cos 120º So, B = 120º |
