Simplify the right side. \\[ \\int \\sin ^{2} 7 \\theta \\sqrt{\\cos 7 \\theta} \\sin 7 \\theta d \\theta=\\int\\left[\\cos ^{1 / 2} 7 \\theta-\\cos ^{5 / 2} \\vee \\quad 7 \\theta\ ight] \\sin 7 \\theta d \\theta \\] Step 3 Substitute \\( \\cos 7 \\theta=u \\). Differentiate with respect to \\( \\theta \\) on both sides. \\[ \\sin 7 \\theta d \\theta=d u \\]