A classmate attempts to derive the relation and writes: 1: For a special case

MATHEMATICS · Single correct · A Level · Mathematics · Trigonometry · Trigonometry

Problem

A classmate attempts to derive the relation

s = r\theta

and writes: Step 1: For a special case, when

s = r

, the subtended angle is

1\,\text{rad}

. Step 2: Therefore, in general,

\theta = \dfrac{s}{\boxed{\phantom{r}}}

. Which quantity should fill the blank box to complete the derivation correctly? (a)

2\pi r

(b)

r

(c)

r^{2}

(d)

s