2cos3xcosx = cos2C + cosC
By Rania Kashi (P3223) on Saturday,
February 24, 2001 - 02:57 pm :
This question has stumped me and its only worth 2 marks!! What
am I missing?? I don't know what to do for it, please help!
2cos3xcosx = cos2C + cosC
Express C in terms of x.
By Kerwin Hui (Kwkh2) on Saturday,
February 24, 2001 - 04:35 pm :
We have
2cosAcosB º cos(A+B)+cos(A-B)
so, substituting A=3x, B=x gives
2cos3xcosx º cos4x+cos2x
so, since the displayed equation holds for all x, we have C=2np±2x
Kerwin