﹙4cosα－3sinα﹚×﹙2cosα－3sinα﹚＝0
则4cosα－3sinα=0或者2cosα－3sinα=0
得tanα=sinα/cosα=4/3或者tanα=sinα/cosα=2/3
所以tan﹙α﹢45°﹚
=(tanα+tan45°)/(1-tanαtan45°)
=(4/3+1)/(1-4/3)
=-7
或者tan﹙α﹢45°﹚
=(tanα+tan45°)/(1-tanαtan45°)
=(2/3+1)/(1-2/3)
=5