(1)利用三角函数的诱导公式对sin2840°+cos540°+tan225°-cos(-330°)+sin(-210°)化简即可求其值;
(2)利用tanβ=,将所求关系式的分母“1”用sin2β+cos2β替换,转换为关于tanβ的关系式即可.
【解析】
(1)∵sin2840°+cos540°+tan225°-cos(-330°)+sin(-210°)
=sin2120°+cos180°+tan45°-cos30°+sin150°
=-1+1-+
=;
(2)∵tanβ=,
∴sin2β-3sinβcosβ+4cos2β
=
=
=.