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a)sin 30°- cos 60°- cos² 120° +sin 135° ×cos 90°

б)tg 30°×tg60°-tg²135°+cos150°

a) sin30°-cos60°-cos^2 120°+sin135°×cos90°=1/2×1/2-(-1/2)^2+0.5√2×0=1/4-1/4=0
б)tg30°×tg60°-tg^2 135°+cos150°=1/√3×√3+tg45°-cos60°=1+1-1/2=1.5