Question 150945
If you need to find an angle when three sides of an oblique triangle are known, use the law of cosines. The equation is:
a<sup>2</sup> = b<sup>2</sup> + c<sup>2</sup> - 2bc cos A
<br> Solve for A
2bc cos A = b<sup>2</sup> + c<sup>2</sup> - a<sup>2</sup>
cos A = (b<sup>2</sup> + c<sup>2</sup> - a<sup>2</sup>)/(2bc)
A = cos<sup>-1</sup>[(b<sup>2</sup> + c<sup>2</sup> - a<sup>2</sup>)/(2bc)]
A = cos<sup>-1</sup>[(14<sup>2</sup> + 15<sup>2</sup> - 13<sup>2</sup>)/(2*14*15)]
A = 53.13&deg