化简cos方(π/4-α)+cos方(π/4+α)

问题描述:

化简cos方(π/4-α)+cos方(π/4+α)

原式=(COSπ/4COSα+SINπ/4SINα)²+(COSπ/4COSα-SINπ/4SINα)²=(√2/2COSα+√2/2SINα)²+(√2/2COSα-√2/2SINα)²=1/2(COS²α+2COSαSINα+SIN²α)+1/2(COS²α-2...