Given #color(white)("XXX")color(red)(9sin^2x) * color(blue)(tan x) = color(red)(16) * color(blue)(tan x)#
#rArr# #{:(tan x=0,color(white)("X")orcolor(white)("X"),9sin^2 x =16),
(rarr x in {0, pi, 2pi,...},,sin^2 x =16/9),
(,,sin x = +- 4/3),
(,,"impossible: " sin x in [-1,+1])
:}#