serif designs released by german foundries fueled by the overwhelming success of futura.the font was released commercially by monotype in 1928 as gill sans. ... 20210311
余弦定理的作用(1)已知三角形的三条边长,可求出三个内角;(2)已知三角形的两边及夹角,可求出第三边.余弦定理是指三角形中任何一边的平方等于其它两边的平方和减去这两边与它们夹角的余弦的积的2倍,即 a2=b2+c2-2bccos a. c2=a2+b2-2abcos c. b2=a2+c2-2accos b.∠c=arccosc