0∫2πsinmx⋅cos4xdx=20487π∵0∫2πsinnx⋅cosmxdx[(n−1)(n−3)(n−5)…1 or 2]x=(m+n)(m+n−2)…1 or 2[(m−1)(m−3)(m−5)…1 or 2]×k Where, k=2π.Both m and n are evenI,otherwiseI=0∫2πsinmxcosnxdx If m=8,n=4, then I=[12⋅10⋅8⋅6⋅4⋅2(7⋅5⋅3⋅1)(3⋅1)]⋅2π=20487π∴m=8