In triangle abc, a = 3, b = 5, and c = 7. find the approximate value of angle a.

This case, where you have 3 given sides and no given angles, requires the use of the cosine law. The cosine law is as follows:



Add your given values to the equation and simplify:








Use your scientific calculator to evaluate. Round the answer to as many decimal places as the question asks:



Hope this helped :)