0

Guest

Courses New

If sin³xsin3x= ∑Cm cosmx where C0,C1...Cn are constants and Cn≠ 0 then n is A. 15 B. 6 C. 1 D. 0 Please refer to the attached image as well.

If sin³xsin3x= ∑Cm cosmx where C0,C1...Cn are constants and Cn≠ 0 then n is
A. 15
B. 6
C. 1 
D. 0
Please refer to the attached image as well.

Question Image
Grade:11

1 Answers

Arun
25750 Points
5 years ago
Dear student
 
sin^3 x = (3 sinx  – sin3x) / 4
 
also
 
sin ax sinbx = ½ (cos(a – b)x – cos (a+b)x)
 
use the above identities
 
sin^3 x sin3x = (3 sinx  – sin3x) * sin3x / 4
 
 = 3/8 (cos 2x – cos 4x ) – 1/8 (cos 0x – cos 6x)
 
 = 1/8 (cos 6x – 3 cos4x + 3 cos2x – cos 0x)
 
Hence n =6
 
 
Hope it helps
 
Regards
Arun (askIITians forum expert)

Think You Can Provide A Better Answer ?

Other Related Questions on Trigonometry

View all Questions »

ASK QUESTION

Get your questions answered by the expert for free

Answer and earn gift vouchers

Win Gift vouchers upto Rs 500/-

View courses by askIITians

Design classes One-on-One in your own way with Top IITians/Medical Professionals

Click Here Know More

Complete Self Study Package designed by Industry Leading Experts

Click Here Know More

Live 1-1 coding classes to unleash the Creator in your Child

Click Here Know More

a Complete All-in-One Study package Fully Loaded inside a Tablet!

Click Here Know More