92 



DYNAMIC METEOROLOGY AND HYDROGRAPHY. 



The vector-addition will be performed according to the simplest law, that of 

 scalar addition or subtraction, in all points where the two given vectors have either 

 the same or opposite directions, i.e., in the points of the curves 



(a) 



(b) 



a. i* 



j8-o 



o 

 32 



(i-a-o , e p. 



Fig. 77. Easily accessible data on the field of the vector-sum. 



A. First given vector (A, a). 



B. Second given vector (B, 0). 



C. Curves a = and a =32, and their points of intersection with the required curves <p =12, 8, 4. 



D. Curves o =0 and a =32 and their points of intersection with the required curves F = 1 1, 10, 9, . . . 



In all points of the first curve the vector-sum F will have the same direction as both 

 A and B,and a numerical value equal to their scalar sum. In all points of the second 

 curve the vector-sum F will have the same direction as the greater of the vectors 

 A and B, and a numerical value equal to their scalar difference. We can therefore 



