Answer:
;
Step-by-step explanation:
First one is half an equilateral triangle. It means the hypotenuse is twice the shorter side, so 2a. Then let's apply the Pythagorean theorem:
At this point is simply take the square root, use the positive value since they're lengths, and rearrange the fraction to have things look nice:
Second one is half a square - or if you prefer, it's an isosceles right triangle, both side lengths are 2. Then its Pythagoras again:
Again, we just have to pick the square roots, and rearrange in a better looking way.