Prove that the orhocenter of a triangle ABC is the incenter of its orthic triangle?

If AD, BE, and CF are the altitudes of an acute triangle ABC, the triangle DEF is called the orthic triangle of triangle ABC. Prove that the orthocenter of triangle ABC is the incenter of its orthic triangle.

Note: Orthocenter is the point at which the three altitudes of a triangle meet. Incenter is the point at which the three angle bisectors meet.

What is a VPN?

VPN is (Virtual Private Network) were first used by companies to enable their employees to securely access internal systems such as email remotely (e.g. from home or while on business trips). Today they are increasingly being used for personal use by individuals to protect their privacy while online in public places (e.g. when using the wi-fi connection in a cafe) or in a country where the internet is censored / blocked (e.g. China, Saudi Arabia��).