21.(2023春•嘉祥县校级月考)求值:3sin220∘−1cos220∘+64sin220∘=\frac{3}{{{\sin }^2}{{20}\circ }}-\frac{1}{{{\cos }^2}{{20}\circ }}+64{\sin ^2}{20\circ }=sin220∘3−cos220∘1+64sin220∘=[ 32 ].