So I was studying some circle properties in Khan Academy and this problem basically states that if:


then find a formula for $S$ in terms of $r$. Now in the problem it says that the angle equals 5.6 radians but then the answer says that:


The problem says this... right below the circle (the angle of the image it's a central angle in radians)

Step 1: A central angle $\theta$ measured in radians tells us how many times the radius fits in the arc

$\text{arc longitude} = \text{radius} * \theta$

Step 2: Substitute

$S= r * 1.2$ <---- ????

Step 3: Formula it's:

$S= r * 1.2$

Why is it 1.2????

Khan Academy radians problem

  • 1
    $\begingroup$ At a first glance, it looks like a typo to me. Certainly I would plug in $\theta = 5.6$ as interpreted from the picture. $\endgroup$
    – Matti P.
    May 14 '20 at 6:06
  • $\begingroup$ Yeah.. damn Khan Academy, I spent like 2 hours looking for an answer when I thought the same at the beginning... xD $\endgroup$
    – Adolf
    May 14 '20 at 6:17
  • $\begingroup$ Perhaps you can send them a message so that they can correct the error. $\endgroup$
    – Matti P.
    May 14 '20 at 6:44
  • $\begingroup$ I always do :3 thanks! $\endgroup$
    – Adolf
    May 14 '20 at 6:50

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