Saved Bookmarks
| 1. |
\left. \begin{array} { l } { A B C , \text { if } ( a + b + c ) ( b + c - a ) = 3 b c } \\ { \text { e that } A = \frac { \pi } { 3 } } \end{array} \right. |
|
Answer» [( b+c ) + a][ ( b+c ) - a] = b² + c² + 2bc -a² (b² + c² - a²) = bc(b² + c² - a²) = 2bc/2(b² + c² - a²)/2bc = 1/2Cos A = 1/2A = 60° |
|