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Trigonometry

Besides the six most common trigonometric functions, there are also some less common or little-used trigonometric functions.

Less Common Trigonometric Functions

The list of some less common trigonometric functions:

1. Versine: Versine is the "versed sine" from one minus the co-function  which is defined as versin(θ)=vers(θ)=1-cos(θ)=2sin2(θ/2).

2. Vercosine: Vercosine is the "versed cosine" from one minus the co-function which is defined as vercos(θ)=1+cos(θ)=2cos2(θ/2).

3. Coversine: Coversine is the "coversed sine" from the co-function of versed sine which is defined as covers(θ)=versin(π/2-θ)=1-sin(θ).

4. Covercosine: Covercosine is the "coversed consine" from the co-function of versed cosine  which is defined as coverc(θ)=vercos(π/2-θ)=1+sin(θ).

5. Haversine: Haversine is the "haversed sine" or "halfed versed sine" which is defined as haversin(θ)=versin(θ)/2=(1-cos(θ))/2=sin2(θ/2).

6. Havercosine: Havercosine is the "haversed cosine" or "halfed versed cosine" which is defined as havercos(θ)=vercos(θ)/2=(1+cos(θ))/2.

7. Hacoversine: Hacoversine is the "hacoversed sine" or "halfed coversed sine" which is defined as hacoversin(θ)=coversin(θ)/2=(1-sin(θ))/2.

8. Hacovercosine: Hacovercosine is the "hacoversed cosine" or "halfed coversed cosine" which is defined as hacovercos(θ)=covercos(θ)/2=(1+sin(θ))/2.

9. Exsecant: Exsecant is the "excepted secant" outside the unit circle which is defined as exsec(θ)=sec(θ)-1.

10. Excosecant: Excosecant is the "excepted cosecant" outside the unit circle which is defined as excsc(θ)=csc(θ)-1.