Найдите площадь круга, диаметр которого 14 см

1. I enjoy competing in sport with others for a price.
This man has competed in Olympic games.
Last year I compete in fancing competition.
2.Our teacher told us to do a research about World War 2.
It's very impotant to do a research about your future job.
Yesterday he did a research about his illness.
3.I was very confused because of this math problem
He was confused because of her behaviour.
I am always confuse on the chemistry classes.