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Trigonometry Angles--Pi/6


TrigonometryAnglesPi6Diagram

Construction of the angle pi/6=30 degrees produces a 30-60-90 triangle, which has angles theta=pi/6 and 2theta=pi/3. From the above diagram, write y=sintheta for the vertical leg, then the horizontal leg is given by

 x=sqrt(1-y^2)=sin(2theta)
(1)

by the Pythagorean theorem. Now use the double-angle formula

 sin(2theta)=2sinthetacostheta
(2)

to obtain

 sqrt(1-y^2)=2ysqrt(1-y^2),
(3)

which can be solved for y=sintheta to yield

 sintheta=1/2.
(4)

Filling in the rest of the trigonometric functions then gives

cos(pi/6)=1/2sqrt(3)
(5)
cot(pi/6)=sqrt(3)
(6)
csc(pi/6)=2
(7)
sec(pi/6)=2/3sqrt(3)
(8)
sin(pi/6)=1/2
(9)
tan(pi/6)=1/3sqrt(3).
(10)

See also

30-60-90 Triangle, Hexagon, Hexagram, Trigonometry Angles, Trigonometry, Trigonometry Angles--Pi/3

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Cite this as:

Weisstein, Eric W. "Trigonometry Angles--Pi/6." From MathWorld--A Wolfram Web Resource. https://mathworld.wolfram.com/TrigonometryAnglesPi6.html

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