Question

sinX=?  cosX=4/5  X apartine (0 grade,90 grade)

Answer 1

sin(x)²+cos(x)²=1
sin(x)²+4÷5²=1
sin(x)²=1-14÷25=9÷25
sin(x)=3÷5

Answer 2

$sin^2x+cos^2x=1\\ sin^2x=1- \frac{16}{25} = \frac{9}{25} \\ sinx=\pm \sqrt{\frac{9}{25}} =\pm \frac{ 3 }{5} \\ Deoarece\ x\in(0^0;90^0)=>sinx=\frac{ 3 }{5}$