CDS Model Paper 2 Mathematics

cos‌x+sec‌x=2 ...(i)
On squaring both sides, we get
cos2x+sec2x+2=4
⇒ cos2x+sec2x=2 ...(ii)
On cubing equation (i), we get
cos3x+sec3x+3(cos‌x+sec‌x)=8
⇒ cos3x+sec3x+(3×2)=8
⇒ cos3x+sec3x=2 ...(iii)
Similarly, when we multiply n in power both sides,cosnx+secnx=2
Alternate Method:
If we put x=0°
then cos‌0°+sec‌0°=1+1=2
Similary cosecnx+secnx
=cosecn0°+secn0°
=1+1=2