求助高数题:证明恒等式arctan1/2+arctan1/3=45度 cos(arcsinx)=根号(1-x^2)在线急等!
问题描述：
求助高数题:证明恒等式arctan1/2+arctan1/3=45度 cos(arcsinx)=根号(1-x^2)在线急等!
答
tan(arctan1/2+arctan1/3)
=[tan(arctan(1/2))+tan(arctan(1/3))]/[1-tan(arctan(1/2))*tan(arctan(1/3))
=(1/2+1/3)/(1-1/2*1/3)=1
arctan1/2+arctan1/3=pi/4
x=sint,-pi/2