Question

Please help me solve this... many thanks!!

Answer 1

The fundamental equation of trigonometry states that

$\cos^2(x)+\sin^2(x)=1$.

This derives from the fact that any point on the unit circle has coordinates $(x,y) = (\cos(x),\sin(x))$, together with the fact that the equation of the unit circle is $x^2+y^2=1$

So, from the fundamental equation you can deduce

$\sin^2(x) = 1-\cos^2(x)$

which in your case leads to

$\sin^2(x) = 1-0.36 = 0.64$