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Question
Find the slope of the line, which makes an angle of 30° with the positive direction of y-axis measured anticlockwise.
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Solution
If a line makes an angle of 30° with the positive direction of the y-axis measured anticlockwise, then the angle made by the line with the positive direction of the x-axis measured anticlockwise is 90° + 30° = 120°.

Thus, the slope of the given line is tan 120° = tan (180° – 60°) = –tan 60° = `-sqrt3`
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