三角比及三角函数英文讲义

trigonometry

1、radian measure

arc length l r θ= area of sector 212A r θ= 2、the basic trigonometry ratio

（a ）in a triangle

（b ）in a unit circle

sin y r

θ= cos x r

θ= tan y x

θ=

（angle measurement ）

3、trigonometry ratio in common use

sin θcos θtan θ6

π3π4π2ππ2π0

4、triangle area

area=12ah area= 1sin 2ab C = 1sin 2bc A = 1sin 2ac B

5、sine rule sin sin sin A B C a b c

== cosine rule 222cos 2b c a A bc +-=222cos 2a c b B ac

+-=222

cos 2a b c C ab +-=

6、double angle formula

sin 22sin cos A A A =

2222cos2cos sin 2cos 112cos A A A A A =-=-=-

22tan tan 21tan A A A

=-

7、trigonometric functions

sin y x = cos y x = tan y x =