1.

Show that \(\begin{vmatrix}sin\,10° & -cos\,10° \\[0.3em]sin\,80° &cos\,80°\end{vmatrix}\) = 1

Answer»

Using, 

sin(A+B) = sin A × cos B + cos A × sin B 

⇒ |A| = sin10° × cos80° + cos10° x sin80° 

|A| = sin(10 + 80)° 

|A| = sin90° 

|A| = 1 

Hence Proved.



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