Cls Jeead-17-18 Xi Mat Target-1 Set-2 Chapter-3

Solution of Assignment (Set-2)

Trigonometric Functions

129

Sol. Answer (4) If 0 <  < 360°, then

cos 



1

⇒

2

 

 3



2

and

3



 3



4 3

 = 120° and 240° 10.. The value of sin15° + cos105° is 10 (1) 0

(2) 2sin15°

(3) cos15° + sin15°

(4) sin15° – cos15°

(3) 1

(4) 0

(3) 0

(4) 1

(3) 1

(4) –1

Sol. Answer (1) sin15° + cos105° = sin15° + cos(90° + 15°) = sin15° – sin15° =0 11.

If sin1 + sin2 + sin3 = 3, then cos 1 + cos2 + cos3 = (1) 3

(2) 2

Sol. Answer (4) sin1 = sin2 = sin3 = 1.

 1  2  3 

 2

12. The va value lue of cos cos10° 10° – sin10 sin10°° is (1) Positive

(2) Negative

Sol. Answer (1) 13.. The valu 13 value e of cos1°. cos1°.cos cos2°. 2°..... ....cos cos179 179°° is (1)) (1

1

(2) 0

2

Sol. Answer (2) cos1°.cos2°……cos179° = 0 (as there will be a term cos 90° in this series whose value is zero) 14. If sec  

(1))  (1

2  3 co cot  13   ,  0     , then the value of  is 2 5  2 4  9 sec   1

15

15

(2)) (2

352

30

352

(3)) (3

5

(4)) (4

352

352

Sol. Answer (1) sec  

13 5

,0   

 2 23

2  3 co cot 



4  9 sec 3/4

=

88/5



2

 1

 =

49

12

5 12 12 5

13

( sec 2   1  tan2  ) 5

15 352

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