گزینه «2» نادرست است، زیرا: $\sin {45^ \circ } = \cos {45^ \circ } = \frac{{\sqrt 2 }}{2} \Rightarrow {\sin ^2}45 = \frac{2}{4} = \frac{1}{2}$$2\cos {45^ \circ } = 2 \times \frac{{\sqrt 2 }}{2} = \sqrt 2  \Rightarrow {\sin ^2}{45^ \circ } \ne 2\cos {45^ \circ }$