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

I need help on these three question's wait for me to upload them thank?

which of the following should ALWAYS be capitalized

Where is Siberia? A. Russia B. Yugoslavia C. Romania D. Greece

What was The Grapes of Wrath based on? A. the Lost Generation authors B. the Harlem Renaissance C. the Dust Bowl D. the Roaring 20s

A 15g bullet travelling at 100m/s strikes and is absorbed by a 75kg object. Find the speed at which the final object moves.

Find the product. 3(m + n)

Environmental science includes the study of all of the following except: a. planets b. soil c. water d. atmosphere

PLZZZZZZZZ HELP ME!!!!!!! Describe how groundwater enters the ground. make sure to discuss the zone of saturation, zone of aeration, and water table

Which type of wave does NOT have a crest? A. a transverse wave B. an oscillating wave C. a longitudinal wave D. an electromagnetic wave

Which of the following statements about the Drug Enforcement Agency (DEA) is true? A. The DEA enforces the Animal Welfare Act. B. The DEA is a division of