To prove the identity (sec²α - 1)cos²α = sin²α, we will manipulate the left-hand side (LHS) of the equation and show that it simplifies to the right-hand side (RHS). Here's the step-by-step proof:
Starting with the LHS:
(sec²α - 1)cos²α
We know that sec²α = 1/cos²α. Substituting this into the LHS, we get:
(1/cos²α - 1)cos²α
Now, we can simplify further:
1/cos²α * cos²α - 1 * cos²α
= 1 - cos²α
Using the trigonometric identity sin²α + cos²α = 1, we can substitute 1 - cos²α as sin²α:
= sin²α
Thus, we have shown that (sec²α - 1)cos²α simplifies to sin²α, which proves the given identity.
Therefore, (sec²α - 1)cos²α = sin²α.