Based on Pythagorean identities, which equation is true?

The Pythagorean identity for cotangent and cosecant is cosecant² θ = cotangent² θ + 1. Rearranging gives cotangent² θ − cosecant² θ = −1, so choice A, “cotangent squared theta minus cosecant squared theta is equal to negative 1,” is true. The secant identity instead gives secant² θ − tangent² θ = 1, not −1.

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