90. Bond Angle in Methane. In the methane molecule, $\mathbf{C H}_{4}$, each hydrogen atom is at a corner of a regular terrahedron with the carbon atom at the center. In coordinates where one of the $C-H$ bonds is in the direction of i + j + k, an adjacent $\mathbf{C}-\mathbf{H}$ bond is in the i – j – k direction. Calculate the angle between these two bonds.

 90. Bond Angle in Methane. In the methane molecule, $\mathbf{C H}_{4}$, each hydrogen atom is at a corner of a regular terrahedron with the carbon atom at the center. In coordinates where one of the $C-H$ bonds is in the direction of i + j + k, an adjacent $\mathbf{C}-\mathbf{H}$ bond is in the i – j – k direction. Calculate the angle between these two bonds.