Вычислите sin70°cos65°-sin25°cos20°.

\[= \frac{1}{2} \cdot \left( \sin{135{^\circ}} + \sin{5{^\circ}} \right) =\]

\[= \frac{1}{2} \cdot \left( \sin(\pi - 45{^\circ}) + \sin{5{^\circ}} \right) =\]

\[= \frac{1}{2} \cdot \left( \frac{\sqrt{2}}{2} + \sin{5{^\circ}} \right) =\]

\[= \frac{\sqrt{2}}{4} + \frac{1}{2}\sin{5{^\circ}}\]