hopefully this can help you
Answered with a tutorial: https://grabcad.com/tutorials/how-do-i-create-rib-on-a-cylinder
Try first to extend your triangle in the cylinder to have a good blend of the two features. Then you can subtract what ever remains from the triangle which sits on the top face of the cylinder... As a result you will have this rib touching fully your main body.
I hope to find this helpful...