1: <problem>
2: <script type="loncapa/perl">
3: $a1 = random(-6,6,4);
4: $a2 = random(-6,6,4);
5: $n1 = random(3,11,2);
6: $n2 = random(2,10,2);
7: $function = "$a1*cos($n1*x)+$a2*sin($n2*x)";
8: $example=&xmlparse('An example would be <m eval="on">$(sin($n1\cdot x)+cos($n2\cdot x))/\sqrt{2}$</m>');</script>
9: <startouttext />
10: Give an example of a function
11: <ol>
12: <li>which is orthogonal to <algebra>$function</algebra> with respect to the
13: scalar product
14: <m>\[<g \mid h> =
15: \frac{1}{\pi} \int_{-\pi}^{\pi}dx g(x) \cdot h(x)\]</m>
16: </li>
17: <li>whose norm is 1.</li>
18: </ol><endouttext />
19: <mathresponse answerdisplay="$example" cas="maxima" args="$function">
20: <answer>overlap:integrate((RESPONSE[1])*(LONCAPALIST[1]),x,-%pi,%pi)/%pi;
21: norm:integrate((RESPONSE[1])*(RESPONSE[1]),x,-%pi,%pi)/%pi;
22: is(overlap=0 and norm=1);</answer>
23: <textline readonly="no" size="50" />
24: <hintgroup showoncorrect="no">
25: <mathhint name="ortho" args="$function" cas="maxima">
26: <answer>overlap: integrate((LONCAPALIST[1])*(RESPONSE[1]),x,-%pi,%pi)/%pi;
27: is(not overlap = 0);</answer>
28: </mathhint>
29: <mathhint name="norm" args="$function" cas="maxima">
30: <answer>norm: integrate((RESPONSE[1])*(RESPONSE[1]),x,-%pi,%pi)/%pi;
31: is(not norm = 1);</answer>
32: </mathhint> <hintpart on="norm">
33: <startouttext />
34: The function you have provided does not have a norm of one.<endouttext />
35: </hintpart>
36: <hintpart on="ortho">
37: <startouttext />
38: The function you have provided is not orthogonal.<endouttext />
39: </hintpart>
40: </hintgroup>
41: </mathresponse>
42: <postanswerdate><startouttext /><p>Note that with respect to the above norm, <m>$\cos(nx)$</m> is perpendicular to <m>$\sin(nx)$</m> and perpendicular to <m>$\cos(mx)$</m> for <m>$n\ne m$</m>.</p><endouttext />
43: </postanswerdate>
44: </problem>
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