Question

what is cos2xcos7x+sin7xsin2x equvivalent to?

cos 9x

sin9x

cos^2(9x)-sin^2(9x)

cos5x

show the work as well

might nwed these formulas

2 sum & Difference Identities sin latb) sina cosb + cos a sinb. Sinca sina cos b-Cosa sinb cos lab) = cos a Casb- sing sinb COSLO-b = cosa cos b+ sino sinb tanla+batang tan b Power reducing Formulas 1 tang tanb sindo - 1-Cosao tanla-b) = tana - tank 1+ tangtanbo cos6= 1+ cosa e Double Angle Identites sin axo a sinx cost tanaal-cosao cos ax = cosay - Sinoy 1+ cos2 = a cosx - 1 Dower reducing - 1-2 sinax sin?a= 1- cas de tanax=2 tanx i tanax Cosa 6 - Icesa e - 2 half-Angle Formulas tan? g=1-casae sinu tul-Logo it cosao Product to sum Formulas 203 - 5 JT Togo sin A CosB = + sin(A+B) sinla-B COSA SinB= [sinLA+B) - SinLA- B J tan 4 = 1- Cosu = sinu COSA cosB / [COBLA+B) + cos(A.B)] sihu iroosu sinA sin B-1/2 [ cool A-B) - COSLA+B) sinu & cos y depend on som to Product Formular Area: ab Sinc sin ut sin v= a sin utvcos - Area-JS (S-a)(5.b)(s) sinu-sinv=2 LOS UV sin Cos U+ Cosv=2cos tv cos uava S=a+b+c Cos U-LOSU=.asin Utv sin way "quadrant

Answer 1

losax Costxt sin7x Sin ax rreisrite of los 7x cos2x & Sin7x Sinax It is in the form of Cos A losB + sinAsin B so Cos 7x les 2x tsin 7csin at - cos (7x-2x) - cos so