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7 0 2 8 * C20-EC-CHPC-PET–102

7028
BOARD DIPLOMA EXAMINATION, (C-20)
SEPTEMBER/OCTOBER—2021
DECE - FIRST YEAR EXAMINATION
ENGINEERING MATHEMATICS – I
Time : 3 hours ] [ Total Marks : 80

PART—A 3×10=30

Instructions : (1) Answer all questions.


(2) Each question carries three marks.

1. If the function f is defined by f (x )  2x 3 , then find the values of


5
(i) f (–2), (ii) f (0) and (iii) f (3).

1
2. Resolve into partial fractions
(x  1)(x  3)

2 3 1   1 2 6
* 3. If A    and B  0 1 3  , then find 2A – 3B.
 0 1 5   

4. Prove that tan  45  A  . tan  45  A   1

3
5. Prove that cos10º cos 50º cos 70º 
8

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6.
*
Find the modulus of the complex number  
.
3 4i 
 5  7i 

7. Find the distance between the two parallel lines 3x – 4y + 7 = 0 and


3x – 4y + 5 = 0.

x 4  16
8. Find lim .
x 2 x  2

9. Differentiate x.secx with respect to x.

10. Differentiate log(1 + tan–1x).

PART—B 8×5=40

Instructions : (1) Answer all questions.


(2) Each question carries eight marks.

2 7 13
11. (a) If A  3 9 4 , find the adjoint and inverse of the matrix.
1 5 3 
OR

(b) Solve the following system of equations using Cramer’s Rule :


x + 2y – z = – 3, 3x + y + z = 4 and x – y + 2z = 6

* 3 2
12. (a) If sin x  sin y  and sin x  sin y  , then prove that
4 5

x y 15 cot x y


8 cot 
2 2
OR

(b) Show that sin1 3  sin1 8  cos 1 36


5 17 85

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13. (a) Solve sin*6 cos 2  sin 5 cos 

OR
c b
(b) In a  ABC, if A = 60º, then prove that   1.
a b c a

14. (a) Find the centre and radius of the circle

3x 2 + 3y 2 – 12x + 6y + 11 = 0

OR

(b) Find the equation of the rectangular hyperbola whose focus is


the point (1, 2) and directrix is the line 3x + 4y – 5 = 0.

 2x   2x 
15. (a) Find the derivative of tan1  with respect to sin1  .


1  x 
2 1  x 2 

OR

(b) If y = sin(log x), then show that x 2y 2 + xy1 + y = 0.

PART—C 10×1=10

Instructions : (1) Answer the following question.


(2) It carries ten marks.

* 16. Find the lengths of tangent, normal, sub tangent and subnormal to
the curve y = x 3 – 2x 2 + 4 at the point (2, 4).

★★★

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