If you angle your vehicle like that, it will still have the 90mm of front armor. There are two ways angles are portrayed ingame:
1. Slopes are calculated into the front armor value. A shell can only penetrate it if it has a higher penetration value. Shell penetration values are based on real life values at 500mm. Range does not affect penetration, but it affects amount of damage after penetration. If you shoot at a plate you cant penetrate, a "ricochet" graphical effect is played.
2. "Angle mod" means that if you shoot at plate at a certain really high angle, the damage is reduced to 0 no matter what. In that case you still get a hitmarker and no ricochet effect, but no damage. This was done to make exploits like shooting at the roof armor from an extremely steep angle impossible.