We know that sin−1(sinθ)=θ, if -\frac{\pi}{2} ≤ θ ≤ \frac{\pi}{2}.
Here, θ = 10 radians which does not lie between -\frac{\pi}{2} and \frac{\pi}{2}.
But, 3\pi - \theta i.e 3\pi - 10 lies, netween -\frac{\pi}{2} and \frac{\pi}{2}.
Also, sin(3\pi - 10) = sin 10.
∴ sin^{-1}(sin 10)=sin^{-1}(sin (3\pi - 10))= 3\pi - 10 |