MH Board · Chapter

Angle and its Measurement

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carry and borrow in sixties, not tens

and

1' = 60''

:

carry and borrow in sixties, not tens

Start

Radian measure

\pi^c = 180^\circ

: multiply by

\frac{\pi}{180}

for radians, by

\frac{180}{\pi}

for degreesLocked

Angles of triangles and polygonsA triangle's angles add to

\pi^c

; each interior angle of a regular

n

-gon is

\frac{(n-2)\pi}{n}

Locked

Arc length $s = r\theta$ with $\theta$ in radians: a pendulum's path is an arcLocked
Area of a sector $A = \frac{1}{2}r^2\theta = \frac{1}{2}rs$ , with $\theta$ in radiansLocked
Angles between clock handsThe minute hand turns $6^\circ$ a minute, the hour hand $\frac{1}{2}^\circ$ :

it gains

5\frac{1}{2}^\circ

a minute

Locked