i'm very newbie, has no basic about vector, etc, but i want to learn

i'm try to create half circle with Inkscape, but my end of half circle looks skewed
you can see in my attachment image.
how to achieve even at the end of circle? so its would be perfect half circle
Thanks
Update image
maybe this image would makes more sense with i want to achieve, as you can see, end of the circle (RED) seems not even so there's a gap with horizontal line (BLUE)
how to make it really even so there's no gap anymore
Thanks