sin250° = sin(360° - 110°) = -sin110° = -sin(90° + 20°) = -cos20° (так как sin(90° + α) = cosα)

cos300° = cos(360° - 60°) = cos60° = 1/2

tg165° = sin165° / cos165° = sin(180° - 15°) / cos(180° - 15°) = sin15° / -cos15° = -tan15° (так как sin(180° - α) = sinα и cos(180° - α) = -cosα)