Question

Mathematics; Ch - Complex number​

Answer 1

Answer:

Correct option is B)

Step-by-step explanation:

sin

3

xsin3x=[

4

3sinx−sin3x

]sin3x[∵sin3x=3sinx−4sin

3

x]

=

4

1

[3sinxsin3x−sin

2

3x]

=

4

1

[

2

3

[cos4x−cos2x]−sin

2

3x]

=

4

1

[

2

3

[cos4x−cos2x]+cos6x−1]

=

8

1

[3cos4x−3cos2x+2cos6x−2]

=

8

1

[−2−3cos2x+3cos4x+2cos6x]

=∑

m=0

n

C

m

cosmx

n=6