of ProjeBilesi 79

Vitiate, the Sum of the T angents of theAngles at the Base, will still be equalthe Tangent of the Angle ffllAt ,made by the Tangent to the Point Aand its Ordinate, -

| DEMON St RAT ION. '

Let 2 =A Yy and L, r and T, as! before: then, ( per Lemma i.) L: 2 ::

b - z : Y x, = AiT—, and {per %)

L i

b Z~- ZZ ^ , ,

2 :- - -. : r : Tj Y A k , equal

y fp _ y 2

-—j — ; but, because b -2 = Y M ,

7 bz — zz ^ ,

o — 2 : ----:: r : 7 , Y Mx } equal

j but the Sum of these Tangents; r J> — rz rz

I L~ +

1 ) t he Tangent of the Angle M At.

&E.D.COR

r b

T '

equal [per Lem.

L