C.4.6—Small-angle approximations

Use small-angle approximations sin θ ≈ θ, tan θ ≈ θ and cos θ ≈ 1 where appropriate, including interference-fringe calculations.

Use c.4.6—small-angle approximations to connect the rule to the data and decision in the question.

This matters because c.4.6—small-angle approximations determines what can be inferred or chosen; begin with the stated conditions and keep the conclusion tied to the evidence.

Example: apply c.4.6—small-angle approximations to one small, clearly defined case, show the key step or comparison, and explain the result in words.

Boundary: C.4.6—Small-angle approximations is not a universal recommendation. Check the syllabus scope, assumptions, units and the limits of the evidence before generalising.