What is sectheta*csctheta secθcscθ in terms of costhetacosθ?

1 Answer
Jan 20, 2016

Step by step working is shown below.

Explanation:

color(blue)(sec(theta)*csc(theta)sec(θ)csc(θ)

We know

color(green)(sec(theta) =1/cos(theta)sec(θ)=1cos(θ)

color(green)(csc(theta) = 1/sin(theta)csc(θ)=1sin(θ)

color(blue)(sec(theta)*csc(theta) = 1/cos(theta)*1/sin(theta)sec(θ)csc(θ)=1cos(θ)1sin(θ)

Note apply the Pythagorean identity

color(green)(cos^2(theta)+sin^2(theta) = 1cos2(θ)+sin2(θ)=1
color(green)(=> sin^2(theta) = (1-cos^2(theta))sin2(θ)=(1cos2(θ))

color(green)(=>sin(theta) = sqrt(1-cos^2(theta))sin(θ)=1cos2(θ)

Our problem would become
sec(theta)*csc(theta) = 1/cos(theta)*1/sin(theta)sec(θ)csc(θ)=1cos(θ)1sin(θ)

color(blue)(sec(theta)*csc(theta) = 1/cos(theta)*1/sqrt(1-cos^2(theta)sec(θ)csc(θ)=1cos(θ)11cos2(θ)

color(blue)(sec(theta)*csc(theta) = 1/(cos(theta)sqrt(1-cos^2(theta))sec(θ)csc(θ)=1cos(θ)1cos2(θ)