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CLASS_11_MATHS_SOLUTIONS_NCERT

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Class XI Chapter 13 – Limits and Derivatives Maths<br />

______________________________________________________________________________<br />

<br />

f x h f x<br />

f ' x<br />

lim<br />

h0<br />

h<br />

cot x h<br />

cot<br />

x<br />

lim<br />

h0<br />

h<br />

lim 1 cos<br />

x<br />

h<br />

cos x <br />

<br />

h0<br />

h <br />

<br />

sin x h<br />

sin x <br />

<br />

1 sin xcos( x h) cos xsin<br />

x h<br />

lim <br />

h0<br />

h sin xsin<br />

x h<br />

<br />

lim 1 sin( x x h)<br />

<br />

<br />

h0<br />

h<br />

sin x sin( x h ) <br />

<br />

1 1 sin( h)<br />

<br />

.lim<br />

sin x h0<br />

h<br />

<br />

sin( x h)<br />

<br />

<br />

1<br />

sinh <br />

1 <br />

. lim lim<br />

sin<br />

x<br />

<br />

h0 <br />

h h0<br />

<br />

sin x h<br />

<br />

<br />

1 1 <br />

.1.<br />

sin x <br />

sin x<br />

0<br />

<br />

<br />

1<br />

<br />

2<br />

sin x<br />

2<br />

cos<br />

ec x<br />

<br />

2<br />

cot x' cos ec x 2<br />

Now, let f2(x) = cosec x. Accordingly, f xh ec x<br />

h<br />

By first principle,<br />

f2x h<br />

f2x<br />

f2<br />

' x<br />

lim<br />

h0<br />

h<br />

1<br />

lim cos ec<br />

x h<br />

cos ecx<br />

h0<br />

h<br />

<br />

lim 1 1 1 <br />

<br />

h0<br />

h <br />

<br />

sin x h<br />

sin x <br />

<br />

1 sin<br />

x sin<br />

x h<br />

lim <br />

h0<br />

h sin xsin<br />

x h<br />

<br />

2<br />

cos<br />

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