steve77 steve77

14-06-2017
Mathematics

contestada

Express cos7xcos2x in the form of A(cosBx+cosCx) where A,B and C are constants to be determined.

Respuesta :

LammettHash LammettHash

15-06-2017

[tex]\cos(7x+2x)=\cos7x\cos2x-\sin7x\sin2x[/tex]
[tex]\cos(7x-2x)=\cos7x\cos2x+\sin7x\sin2x[/tex]

[tex]\implies\cos9x+\cos5x=2\cos7x\cos2x[/tex]
[tex]\implies\cos7x\cos2x=\dfrac12(\cos9x+\cos5x)[/tex]
[tex]\implies A=\dfrac12,B=9,C=5[/tex]

Answer Link

Otras preguntas

Can someone help me with this math homework please!

I ______ he would come(hope/hopes/hoped/hoping)

The current loop lies flat on a horizontal surface. Facing the loop from the top, the current moves in a clockwise direction. Which way does the magnetic field

Why is solving the pollution problem hard and expensive and difficult?

The part dimension for an injection-molded part made of polycarbonate is specified as 4.00 in. Compute the corresponding dimension to which the mold cavity shou

What l have learned How will you improve your decision making write at least 5 things that you certainly can apply in yourself

Hii pls helpnme to write out the ionic equation

Suppose you are among those who believe that the NLRA should be transformed. What arguments support the claim that a complete overhaul is necessary

The claim that 40% of those persons who retired from an industrial job before the age of 60 would return to work if a suitable job was available is to be invest

5 importance of Computer in a modern offices