Question

Evaluate this question and dp tell me how did u do this

Answer 1

Answer:

Step-by-step explanation:

Toolbox:

The determinant of a square matrix of order 2×2 is |A|=a11×a22−a12×a21

cos(A+B)=cosAcosB−sinAsinB

cos90∘=0

Let Δ=∣∣∣cos15∘sin75∘sin15∘cos75∘∣∣∣

on expanding we get,

Δ=cos15∘cos75∘−sin15∘sin75∘

This is of the form cos(A+B)=cosAcosB−sinAsinB

Therefore cos15∘cos75∘−sin15∘sin75∘=cos(15+75)

=cos90∘

But cos90∘=0

Therefore Δ=0