25.如圖,梯形ABCD中,AD∥BC,AB=26,BC=42,cosB=
,AD=DC.點(diǎn)M在射線CB上,以點(diǎn)C為圓心,CM為半徑的⊙C交射線CD于點(diǎn)N,聯(lián)結(jié)MN,交射線CA于點(diǎn)G.
(1)求線段AD的長(zhǎng);
(2)設(shè)線段CM=x,
=y,當(dāng)點(diǎn)N在線段CD上時(shí),試求出y關(guān)于x的函數(shù)關(guān)系式,并寫出x的取值范圍;
(3)聯(lián)結(jié)DM,當(dāng)∠NMC=2∠DMN時(shí),求線段CM的長(zhǎng).