Inaccurate results for trigonometric functions with exact results

[Wazhai]

Describe the bug
The below examples of the trigonometric functions show a correct result at first. However, subtracting that result from itself results in a non-zero value, which shows that the results are represented as incorrect approximations internally, when it should be an exact result.

In DEG mode:
arcsin(1) - 90 != 0
sin(30) - 0.5 != 0
In RAD mode:
sin(π/2) - 1 != 0
but interestingly: cos(±π) + 1 == 0

This is a new issue spawned from the similar issue #222.

Steps To Reproduce

1. Try the above calculations in scientific mode

Expected behavior
Exact internal representation and result 0 for above calculations.

Device and Application Information (please complete the following information):

• OS Build: 10 0 17763 0
• Architecture: X64
• Application Version: 10.1812.10048.0

[MicrosoftIssueBot]

This is your friendly Microsoft Issue Bot. I've seen this issue come in and have gone to tell a human about it.

[uhliksk]

Some situations are not solvable by any conventional way, for example sin ( 42 ) - ( sqrt( 30 + sqrt( 180 ) ) - sqrt( 5 ) + 1 ) / 8 in DEG mode.

[grochocki]

Thanks for creating the report! We should defintiely try to squash these.