Given,
![](https://www.sarthaks.com/?qa=blob&qa_blobid=5882780906735209806)
Now expanding along R1, we get
△ = -(-a + sin x) [-a2 - a sin x-1- cos x] + (1 + cos x) [-a - sin x + a + a cos x]
= -[a3 + a2 sin x + a + a cos x - a2 sin x - a sin2 x - sin x - sin x cos x] + [a cos x - sin x- sin x cos x + a cos2 x]
= -a3, which is independent of x.