C-10-Q045mediumsingle_mcqcos45∘=?\cos 45^\circ = ?cos45∘=?a111b12\dfrac{1}{\sqrt{2}}21c32\dfrac{\sqrt{3}}{2}23d12\dfrac{1}{2}21ব্যাখ্যাcos45∘=12\cos 45^\circ = \dfrac{1}{\sqrt{2}}cos45∘=2, the same as because the isosceles right triangle is symmetric. This is a standard memorized value.