Find dy
dx
, if y = 12 (1 – cos t), x = 10 (t – sin t), 
2
2
t
π
π
−
< <
13 Find dy
dx , if y = sin–1 x + sin–1 
2
1
−x
, 0 < x < 1
14 If 
1
1
0
x
y
y
x
+
+
+
=
, for , – 1 < x < 1, prove that
(
)2
1
1
dy
dx
x
= −
+
15 If (x – a)2 + (y – b)2 = c2, for some c > 0, prove that
3
2
2
2
2
1
dy
dx
d y
dx




+







is a constant independent of a and b