Definite integral approximation using Trapezoidal Rule

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By simply drawing a graph of the function, I can find that whenever the function is concave up, the trapezoidal rule gives me a definite integral approximation larger than the actual integral of the function;whenever the function is concave down, the trapezoidal rule gives me a definite integral approximation smaller than the actual integral of the function. Is there any way to prove it true other than drawing out the function graph?