sin²a+sin²75°=1,且a为锐角,则a=_______

sin²a+sin²75°=1,且a为锐角,则a=_______
sin²a+sin²75°=1,且a为锐角,则a=_______

sin²a+sin²75°=1,且a为锐角,则a=_______
解由sin²a+sin²75°=1
又由cos²75+sin²75°=1
即sin²a=cos²75
即sina=cos75°
即sina=cos(90°-15°）=sin15°
即a=15°.