fixed inflow_angle bug and power sum bug

[jefalon]

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Purpose

This PR fixes a bug with the inflow angle. Additionally, this should fix #78.

Type of change

Select the appropriate type(s) that describe this PR

• Bugfix (non-breaking change which fixes an issue)
• New feature (non-breaking change which adds functionality)
• Breaking change (non-backwards-compatible fix or feature)
• Code style update (formatting, renaming)
• Refactoring (no functional changes, no API changes)
• Documentation update
• Maintenance update
• Other (please describe)

Testing

No new testing is needed, though we might want to add a multiangle regression test in the future rather than it just being a demo

Checklist

Put an x in the boxes that apply.

• I have run existing tests which pass locally with my changes
• I have added new tests or examples that prove my fix is effective or that my feature works
• I have added necessary documentation