Q17 of 110 Page 258

Evaluate

cos15°cos75° - sin75°sin15°

= cos(15°+75°) ∵ cosAcosB-sinAsinB=cos(A+B)

= cos90°

= 0

∵ cosAcosB-sinAsinB=cos(A+B)

Evaluate

Without expanding the determinant, prove that

SINGULAR MATRIX A square matrix A is said to be singular if |A| = 0.

Also, A is called non singular if |A| ≠ 0.