ap physics B help.
问题描述：
ap physics B help.
vector A has a magnitude of 10 units and makes an angle of 30degree with the horizontal x-axis.vector B has a magnitude of 25 units and makes an angle of 50degree with the negative x-axis.what is the magnitude of the resultant between these two vectors?
A.20
B.35
C.15
D.45
E.25
(本题出自barron AP physics B page 62-5)
答
余弦定理谢谢，用余弦定理成功了但是如果画出图形，就是等腰了，图中有一个100度，不就矛盾了么？一个10 units 一个25 units 怎么会是等腰呢。不可能的吧。注意他们的夹角。