Resize the featured image inside a post

Hi, First,many thanks for this great theme! Second,I added the featured image to the post,and successfully get it displayed on homepage slider.The size of image inserted was 1140px*450px as I wanted it to fit in the slider,but the problem is that the image has been truncated in the post page. Is it possible to make the image displayed as 700px*245px in post page while keeping the same size of 1140px*450px in homepage slider? Thanks in advance.