1)sin30°×cos60° = (1/2) × (1/2) = 1/cos² 120° = cos(180° - 120°) = -cos60° = -1/sin135° = sqrt(2)/cos90° = 0
1/4 - (-1/2) + sqrt(2)/2 × 0 = 1/4 + 1/2 = 3/4
2)tg30° = sqrt(3)/tg60° = sqrt(3tg135° = -cos 150° = cos(180° - 150°) = -cos30° = -sqrt(3)/2
sqrt(3)/3 × sqrt(3) - 1 + sqrt(3)/2 = 3/3 - 1 + sqrt(3)/2 = 1 - 1 + sqrt(3)/2 = sqrt(3)/2
1)
sin30°×cos60° = (1/2) × (1/2) = 1/
cos² 120° = cos(180° - 120°) = -cos60° = -1/
sin135° = sqrt(2)/
cos90° = 0
1/4 - (-1/2) + sqrt(2)/2 × 0 = 1/4 + 1/2 = 3/4
2)
tg30° = sqrt(3)/
tg60° = sqrt(3
tg135° = -
cos 150° = cos(180° - 150°) = -cos30° = -sqrt(3)/2
sqrt(3)/3 × sqrt(3) - 1 + sqrt(3)/2 = 3/3 - 1 + sqrt(3)/2 = 1 - 1 + sqrt(3)/2 = sqrt(3)/2