Hello!
Diagram: it's a Toblerone box except it's a right-angled triangle instead of an equilateral triangle, tilted so that it's balancing on its spine (ie resting on the edge connecting the two right angles)
AED is a right-angled triangle, so for the first part you just use Pythagoras.
AE squared + ED squared = x squared. But AE=AD as it's an isosceles triangle,
so 2(AE squared) = x squared,
AE squared = 0.5xsquared
and AE = x/(root 2) also ED = x/(root 2)
Area of triangle = 0.5 x AE x ED
Area of triangle = 0.5 multiplied by x/(root 2) multiplied by x/(root 2)
which gives area of triangle = 0.5 (x squared)/2 = (x squared)/4
First part done.
Second part in a minute.
love Danniella