对于某些物理问题,虽然具体情境不同,但其极值或临界值的条件常与某个角度有关.这样特殊的角度有三个,它们是arccos53,arccos32和arccos32,其独特魅力耐人寻味.(1)cosθ=53,θ=53°,这个角度是以勾股数3、4、5为边的直角三角形中数值为5的斜边与数值为3的直图1角边的夹角,如图1 For some physical problems, although the specific situation is different, the condition of the extreme or critical value is often related to an angle. There are three special angles such as arccos53, arccos32 and arccos32. Their unique charm is thought-provoking. (1) Cosθ=53, θ=53°, this angle is the angle between the hypotenuse with a value of 5 in a right-angled triangle with sides 3, 4, and 5 and the angle of a corner of a straight graph with a value of 3, as shown in Fig. 1