Inverse trigonometric ratios: cosecant, secant and cotangent

In this section, we are going to define the inverse trigonometric ratios, this is, the inverse ratios of the sine, the cosine and the tangent. Given a triangle rectangle, we define the cosecant, the secant and the cotangent of an angle x as the inverse ratios of the sine, the cosine and the tangent, respectively.

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  • csc(x): the cosecant is the inverse of the sine or, also, its multiplicative inverse: csc(x)=1sin(x)=ca

  • sec(x): the secant is the inverse of the cosine or, also, its multiplicative inverse: sec(x)=1cos(x)=cb

  • cot(x): the cotangent is the inverse of the tangent or, also, its multiplicative inverse: cot(x)=1tan(x)=ba

Example

Given the triangle of sides a=3, b=4 and c=5, we are going to compute the trigonometric ratios associated with such a triangle.

Then: sin(x)=35cos(x)=45tan(x)=34

The associated inverse trigonometric ratios are: csc(x)=53sec(x)=54cot(x)=43

Example

Given the triangle of sides a=5, b=12 and c=13, compute its trigonometric ratios.

sin(x)=513=cos(x)=1213tan(x)=512

csc(x)=135sec(x)=1312cot(x)=125