求y=(sinx)^2+3sinxcosx+4(cosx)^2 (0扫码下载作业帮搜索答疑一搜即得
问题描述：
求y=(sinx)^2+3sinxcosx+4(cosx)^2 (0 扫码下载作业帮
搜索答疑一搜即得
答
y=(sinx)^2+3sinxcosx+4(cosx)^2 = 1+3(cosx)^2 + 3sinxcosx = 1 + 3/2*[2(cosx)^2-1+1] + 3/2*2sinxcosx = 1 + 3/2cos2x + 3/2 +3/2sin2x = 5/2 + 3/2(sin2x + cos2x ) = 5/2 + 3/2*根号2*sin(2x+ pi/4 )由0