Q. Inverse circular functions,Principal values of sin−1x,cos−1x,tan−1x.
tan−1x+tan−1y=tan−1x+y1−xy, xy<1
π+tan−1x+y1−xy, xy>1.
(a) If cos−1p+cos−1q+cos−1r=π, then prove that
p2+q2+r2+2pqr=1
(b) If sin−1x+sin−1y+sin−1z=π, then prove that
x4+y4+z4+4x2y2z2=2(x2y2+y2z2+z2x2)
(c) If tan−1x+tan−1y+tan−1z=π or π/2 show that
x+y+z=xyzor xy+yz+zx=1.