The value of $| \begin{matrix} c o s 40^{\circ} & s i n 40^{\circ} \\ s i n 20^{\circ} & c o s 20^{\circ} \end{matrix} | = ?$

Question

Question

Answer 1

Concept:

Formula used

cos(A + B) = cosA.cosB – sinA.sinB

Calculation:

$| \begin{matrix} c o s 40^{\circ} & s i n 40^{\circ} \\ s i n 20^{\circ} & c o s 20^{\circ} \end{matrix} |$

= cos 40°.cos 20° – sin 40°.sin 20°

= cos (40° + 20°)

= cos 60°

= 1/2