a. Draw a sketch of the graph y = sin x and use it to demonstrate why sin x = sin (180° − x).

b. By referring to the graphs of y = cos x and y = tan x, state whether the following are true or false.

i. cos x = cos (180° − x) 

ii. cos x = −cos (180° − x)

iii. tan x = tan (180° − x)

iv. tan x = −tan (180° − x)