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eg : tg i: y : z and eg : -J- F' tz : : y : x, or
c : t : : y : z, and c 1 : F l tz i : y : x
From the first of these proportions, we
i t k
nave, — = —
7 c y
t 3
or, — = —
C f
or, by taking 1 from each side,
t 1 —c* z 7 —jr*
but
z a ~y 2
f
t'-CP
or,
r
X*
7
x
and from the second,
F Hk _ x
c* j
But from the preceding equation,
X
y
F ‘tk
C
or F l tz — c^/f _ c %
Hence, by taking the fluxion of each side,
cti
tz
V>
Ct
Vt l