A channel has a trapezoidal cross section. The canal is 1.3 meters deep, 1.5 meters wide at the bottom and 2.6 meters wide at the mouth. What is its cross-sectional area in square meters?
一条水渠的横截面是梯形．渠深1.3米，渠底宽1.5米，渠口宽2.6米．它的横截面的面积是多少平方米？
<gadget id="calculator">2.6 + 1.5</gadget>
<output>4.1</output>

<gadget id="calculator">1.3 / 2</gadget>
<output>0.65</output>

<gadget id="calculator">4.1 * 0.65</gadget>
<output>2.665</output>

<result>2.665</result>