对于一个底边在x轴上的三角形，采用斜二测画法作出其直观图，其直观图面积是原三角形面积的______倍．
设底边在x轴上的三角形的底边长为a，高为b，其面积为S=
ab．1 2
采用斜二测画法作出其直观图得到的三角形的底边长为a，高为
a•sin45°=1 2
a，2 4
其面积为S′=
×(2 4
ab)，1 2
∴其直观图面积是原三角形面积的
倍．2 4
故答案为：
．2 4
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