we can have a triangle and we know that there are two angles. 
 30º and a 45º + 105 =180º angle. applying the sides. 
 therefore if we have the whole triangle completed we have a constant triangle. 
 
 so it tell us we can you’se SOH CAH TOA 
 we can varrify what kind of triangle we are using. 
 
 for example if we were to use Sin I would do 
 
 Sin 30/ 2 = sin of 105º/ A = sin=45º/ B
 
 if you would want to solve for sin 30/2 and sin 105, then we solve. 
  
 or Sin 30/2 and Sin 105 as well. 
 
 with your calculator use sin= 30=.5 and use sin 105º a divide by 1.5 on both sides 1.5= A /sin 105º * 1.5 answer would be 3.86. a is = to 3.86 (Not the answer)