餘弦定理(3)
Author: 藍邦偉  老師

B(x,y)

a

A(b,0)

c

B(x,y)=[a,\angle{C}]=(acosC,asinC)

c²= \overline{ AB }² 

=(acosC-b)²+(asinC-0)²

餘弦定理

=a²cos²C+a²sin²C-2abcosC+b²

=a²+b²-2abcosC

b

u = Vector((x(Corner[1.0]), 0.0), (x(Corner[3.0]), 0.0))
v = Vector((0.0, y(Corner[1.0])), (0.0, y(Corner[3.0])))
C = (0, 0)
C_1 = (3.7800000000000002, 3.52)
b = Segment(C_1, C)
A = Point(xAxis)
b_1 = Segment(C_1, A)
α = Angle(A, C, C_1)
c = Segment(C, A)
r, c_1, a, b_2 = Polygon(C, A, C_1)
文字7: "=" + (a^(2.0)) + "+" + (b^(2.0)) + "-2\times{}" + b + "\times{}" + c + "cos" + α
文字8: "=" + (c^(2.0))
文字10: "\rightarrow{}c=" + c