唔係記得中四好多..
畢氐定理:a*a+b*b=c*c
(a+b)(a+b)=a*a+2ab+b*b
cos law:a*a=b*b+c*c-2bc(cosA) (大楷A係一個角,細楷係邊長)
sin law:a/sinA=b/sinB=c/sinC
slope:(y1-y2)/(x2-x1)
Heron's formula:Area of △=√[s(s-a)(s-b)(s-c)],where s=(a+b+c)/2
Area of △=1/2(b)(c)(sinA)
角度generanal form:Tanθ=180°n+α(α=Tanθ的逆運算)
Cosθ=360°n±α
Sinθ=180°n+(-1)nα(-1後面個n係-1既次方)