Thread: basic trigonometry problems, help?

given cos θ = 3/5, tan θ < 0
find:
sin 2θ
cos 2θ
cot 2θ

use half measure identities to find exact values of the following:

tan 15 degrees
sec π/12


THANK YOU SO MUCH!

Originally Posted by pongpong

given cos θ = 3/5, tan θ < 0
find:
sin 2θ
cos 2θ
cot 2θ

use half measure identities to find exact values of the following:

tan 15 degrees
sec π/12


THANK YOU SO MUCH!

Since cos is positive and tan is negative , so the angle will be in quadrant 4 . Draw a triangle in quadrant 4 and find sin and tan .

Originally Posted by pongpong

use half measure identities to find exact values of the following:

tan 15 degrees

tan 15 = tan 1/2(30)

You can use this identity .



where is 30 .

In this case , is in the first quadrant so it will be positive .