If 3sinx+4cosa x=7 has at least one solution then the possible values of a
4m4n+1,m,n∈Z
4n+1π2,n∈Z
m4n+1,m,n∈Z
4n+14m,m,n∈Z
We have sinx=1,cosa x=1⇒a x=2mπ,x=(4n+1)π2,m,n∈Z
⇒(4n+1)π2=2mπa⇒a=4m4n+1,m,n∈z