What do the graphs of sine and cosine have in common with the swinging you see? Which reasons did you think of? Answer: The high and low points repeat in a pattern. The cycle repeats at equal time intervals. The swinging motion is smooth, unabrupt.
The relationship between the cosine and sine graphs is that the cosine is the same as the sine — only it’s shifted to the left by 90 degrees, or π/2. The trigonometry equation that represents this relationship is: cosx= sin (x+π/2)
The graphs of the sine and cosine functions illustrate a property that exists for several pairings of the different trig functions. The property represented here is based on the right triangle and the two acute or complementary angles in a right triangle. The identities that arise from the triangle are called the cofunctionidentities.
