sinx=45\sin x = \dfrac{4}{5}sinx=54 から cosx=35\cos x = \dfrac{3}{5}cosx=53 (1) sin2x=2sinx⋅cosx=2⋅45⋅35=2425\sin 2x = 2\sin x \cdot \cos x = 2 \cdot \dfrac{4}{5} \cdot \dfrac{3}{5} = \dfrac{24}{25}sin2x=2sinx⋅cosx=2⋅54⋅53=2524 (2) cos2x=1−2sin2x=1−2⋅(45)2=1−3225=−725\cos 2x = 1 - 2\sin^2 x = 1 - 2 \cdot \left(\dfrac{4}{5}\right)^2 = 1 - \dfrac{32}{25} = -\dfrac{7}{25}cos2x=1−2sin2x=1−2⋅(54)2=1−2532=−257 (3) tan2x=sin2xcos2x=−247\tan 2x = \dfrac{\sin 2x}{\cos 2x} = -\dfrac{24}{7}tan2x=cos2xsin2x=−724