Find (1 - sin² θ) (tan²θ + 1) - 1.

​$$(1 - \sin^2 \theta)(\tan^2 \theta + 1) - 1$$​​

​$$1 - \sin^2 \theta = \cos^2 \theta \\\tan^2 \theta + 1 = \sec^2 \theta$$​​

Substituting the identities into the expression:

​$$(1 - \sin^2 \theta)(\tan^2 \theta + 1) - 1\\ = \cos^2 \theta \cdot \sec^2 \theta – 1\\ =1 - 1 \\= 0$$​​

Thus, the value of the expression is 0.