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to be orthogonal to the line connecting the acoustic sources
(Li), and thus the slope of line L2 is
(8) m = (Y2 YI)/(X2 Xl)
Line L2 bisects line Li at a point whose (Y,X) coordinates are ((Y1 + Y2)/2, (Xl + X2)/2), so from equation (7) the X' intercept of line L2 is
(9) b = (Xl + X2 m(Yl + Y2))/2
The equation describing the screen is
(10) X2 + y2= 1
since the screen radius is defined as 1 rad. The X coordinate of the intersection of line L2 with the screen, from equations (7) and (10), is then
(11) XP = b + mYp = (i (yp)2)
Squaring both sides of equation (ii) and solving the resulting quadratic equation for Yp, the Y coordinate of the intersection of line L2 with the screen is
(12) Yp = (- bm (m2 b2 + 1) )/(m2 + 1)
There are two values for Yp corresponding to two possible intersections of line L2 with the screen. Since it is known that the subject's line of sight is always in the positive direction with regard to the Y axis, the greater value of Yp is the only one of interest. In addition, if the radical in equation (12) is defined as
(13) S = (m2 b2 + 1)
then equation (12) becomes
(14) Yp= (- bm + S)/(m2 + 1)
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