定语从句（5）
2、“单个介词+which”不处于从句句首的情况，它在从句中作定语而不是作状语(这是难点，目前不作要求) a2 + b2 = c2 is the equation(方程) to a circle(圆) the coordinates(坐标) of points(点) on which could be written as (c cos x, c sin x).
The mathematicians(数学家) of the middle of the nineteenth century(十九世纪) formulated(对…列出方程) a problem in the calculus of variations (变分学) the answer to which seemed (似乎) to them self-evident(自明的). This equation(方程) is of the form (形式) dx(t)/dt + ax(t) = b, the solution (解) to which is x(t) = b/a + Ae-at. The corresponding(相应的) quantity(量) that describes(描述) a magnetic field(磁场) is called its magnetic(磁的) induction(感应强度), the symbol(符号) for which is B.
“Parallel”(平行) is used here to refer to (指) two straight(直的) lines, the distance between which remains(保持) the same. No part of this publication(出版物) may be reproduced (翻印) or transmitted (传播) in any form(形式) or by any means(手段) without the written(书面的) permission(允许) of the copyright(版权) holder(拥有者), application(申请) for which should be addressed(写信) to the Publishers(出版社).
The open end(开口端) of the tube (管子) is connected(连接) to the apparatus(装置) the pressure(压力) within which is to be measured(测量).