sin(π/4－x)＝5/13,0＜x＜π/4,则 cos2x/cos(π/4－x)＝?

已知-π/2＜x＜0,sin x+cos x=1/5求sin 2x+2 sin sin(π/4－x)＝5/13,0＜x＜π/4,则 cos2x/cos(π/4－x)＝? 已知sin(π／4－x﹚＝5／13,0＜x＜π／4,求[cos2x]／[cos﹙π／4＋x﹚]的值 三角函数的问题 (21 13:38:6)已知－(π/2)＜x＜0,sin x+cos x=1/5求sin x－cos x 的值 sin x = 5/13 且 0°＜x＜90°,求tan(-X) 请问记得您以前做过的这个题么已知cos(π/4+x)=5/13,0＜x＜π/4,求sin(π/4-x)/cos2x因为π/4+x和π/4-x是互余的（和是π/2）,所以cos(π/4+x）=sin(π/4-x)=5/13因为0＜x＜π/4所以sin(π/4+x)=12/13 (因为π/4+x为第一 已知sin(π/4--x)=5/13,0 已知sin(π/4-x)=5/13,且0 已知0＜x＜π/4,sin(π/4-x)=5/13,求cos2x/cos(π/4+x)的值 已知0＜x＜π/4,sin(π/4 -x)=5/13,求cos2x除以cos(π/4 +x)的值 已知0＜x＜π/4,sin(π/4-x)=5/13,求(cos2x)/(cos(π/4+x))的值. 已知cos(π/4+x)=5/13,0＜x＜π/4,求sin(π/4-x)/cos2x超急的! 一道数学三角函数题目,0＜x＜四分之π sin(π/4-x)=5/13 求cos2x/cos(π/4+x) 已知0＜x＜45,sin(45－x)＝5/13,求cos2x/cos(45＋x)的值 sin(x+π/4) 求人解题：已知sin（π/4－x）=5/13,0＜x＜π/4,求[cos（2x）]/[cos（π/4＋x）]的值 ．已知sin x＋cos x＝ (0≤x＜π),则tan x的值等于 解方程：2sin²（x／2)＋5sin(x／2)－3＝0