Contact us
Choose a category below so we can get back to you as quickly as possible.
這個等式是成立的 根據二倍角公式: cos2a=(cosa)^2-(sina)^2 再根據(cosa)^2+(sina)^2=1即(sina)^2=1-(cosa)^2 帶入得cos2a=2(cosa)^2-1 把a換成a-π/3就得到了 cos2(a-π/3)=2[cos(a-π/3)]^2-1 (編輯個公式真費勁)
We and our partners use cookies and other technologies to analyze traffic and optimize your experience. View more info and control your cookies settings at any time in our Cookies Policy.