T R I 



NGMETay. C Woodhouse, Barlow.) 



I. PLANE TRIGONOMETRY. 

 Solution of the cases of right angled triangles. 



"Lst a be the base, b the perpendicular, c the hypothenusa, and A, B, 

 C the angles opposite. 



Solution of the cases of oblique angled triangles. 

 Let a, b t c be the sides of the A ; A, B, C the '* opposite to them. 



Cote I. 



Given two sides and an / opposite to oue of them j or two /'a and a 

 side ; to find the rest. 



Solution. The sides are proportional to the sines of the opposite /'s. 



Note. When two sides and an / opposite to one of them art given, the 

 case is sometimes ambiguous, viz. when the side adjacent is greater than, 

 the side opposite to the given ^, and that ^ is acute. But in practical 

 cases there will be found some circumstance or other to remove tlie 

 .ambiguity. 



Case 2. 



Given two sides a and b, and included ^ C. 



Solution 1st. Tan. -~ - ^LrA Tan. A ^"--' Hence A + B 



and A B are known, and consequently A and B. 

 321 



