log10sinx+log10cosx=−1
⇒log10(sinxcosx)=−1
⇒log10(sin2x2)=−1
⇒sin2x2=110
⇒sin2x=15 ⋯(1)
And, log10(sinx+cosx)=(log10n)−12
⇒2log10(sinx+cosx)=log10n−log1010
⇒log10(sinx+cosx)2=log10(n10)
⇒(sinx+cosx)2=n10
⇒1+sin2x=n10
Using equation (1), we get
1+15=n10
⇒n=12