fix(trigonometry): add arcsin() function

[tysoncung]

Problem

Issue #110 requested an arcsin() function in trigonometry.py to complement the existing sin() and arctan() functions.

Solution

Implemented arcsin(x) using the identity:

arcsin(x) = arctan(x / sqrt(1 - x²))

This leverages the existing arctan() and the algebra.sqrt() functions already in the codebase, keeping the implementation consistent with the project's style.

Behaviour

• Accepts float | int input in the range [-1, 1]
• Raises ValueError for inputs outside the valid domain
• Handles edge cases x = 1 → π/2 and x = -1 → -π/2 directly
• Returns the result in radians

Files Changed

• simple_equ/geometry/trigonometry.py — added arcsin() function with full docstring

Verification

from simple_equ.geometry.trigonometry import arcsin
import math

arcsin(0)    # 0.0
arcsin(0.5)  # ≈ 0.5236 (π/6)
arcsin(1)    # ≈ 1.5708 (π/2)
arcsin(-0.5) # ≈ -0.5236

Closes #110

[antfullstack]

Thank you! That will be merged, really appreciate your time and effort!