sin7°cos37°-sin83°sin37°的值是多少?3Q

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sin7°cos37°-sin83°sin37°的值是多少?3Qsin7°cos37°-sin83°sin37°的值是多少?3Qsin7°cos37°-sin83°sin37°的值是多少?3Q=cos

sin7°cos37°-sin83°sin37°的值是多少?3Q
sin7°cos37°-sin83°sin37°的值是多少?3Q

sin7°cos37°-sin83°sin37°的值是多少?3Q
=cos83°cos37°-sin83°sin37° =cos(83+37) =cos120° =-1/2

原式=cos83°cos37°-sin83°sin37°=cos(83°+37°)=cos120°=-1/2