Mathematics for IGCSE & O level - Pythagoras' Theorem And Trigonometry (Section 3 - No. 40)
Which of the following statements about the cosine function is true?
It is always positive.
Its range is from 0 to 1.
Its range is from -1 to 1.
It is always negative.
解释
The range of the cosine function is [-1, 1].