At an angle of 45°, we look both up and out, and this is a good paradigm for life. At 45° degrees, we can view both up: seeing and loving God, and out: seeing and loving our neighbor.
At 90° (i.e., straight up or straight out) our field of vision misses either God or the people whom He loves. For example, if I look straight up (90°) I am looking toward God but not toward the people He loves; if I look straight forward (90°) I am looking toward the people I love but not toward the God I love. At a 45° angle, I can see them both.
The Christian life should be lived at 45°. A life directed only to God but oblivious to our neighbor is incomplete, for it lacks the second table of the Law (love of neighbor). A life wholly devoted to man and humanitarian endeavors but forgetful of God is not spiritual at all; it is mere social activism and neglects the first table of the Law (love of God). It is at 45° that we find the proper balance for life.
Here is an interesting video that takes up this theme:
Another mathematical way of looking at Christian life is the equation 1×3.
1 being the virtue of love, 3 being object of love: self, neighbor, and God.
Why does faith require metaphor?
Matthew 13:10-17