that's because Cosine is adjacent to the angle (the angle being 30 degrees and the side next to it is 43mm) divided by the hypotenuse (longest side of a right triangle. The 50 mm). A way you can remember the sin, cosine and tangent is SOH CAH TOA. Sine=opposite over hypotenuse, Cosine = adjacent over hypotenuse, Tangent = opposite over adjacent. For the next one, it is the same principal. X is adjacent to 22 degrees and the other number is the hypotenuse so it has to be Cosine.
One box has 15 flavor And 1 child gets 3 flavors So 1 box is enough for 5 children by dividing 15 by 3 There are 25 children so 25/5 = 5 So, Raymond has to buy 5 boxes
