The four sp³ hybrid orbital of equivalent energies and shape with 25% s character and 75 % p character, directed to form four corners of the tetrahedron  in case of CH₄ . The angle between tetrahedron formed is -

In the case of methane there is mixing of one s and three p orbitals of the valence shell to form 4 sp³ hybrid orbitals of equivalent energies and shape. In order to retain in shape and form a stable geometry all bonds are distant at an angle of 109.5 degree and thus form 4 corners of tetrahedron.