Posted by Kaleen on Saturday, March 10, 2012 at 9:17pm.
Use one of the identities
cos(t + 2πk) = cos t or sin(t + 2πk) = sin t
to evaluate each expression. (Enter your answers in exact form.)
csc(2π − 2π/3)
- Precalculus - Reiny, Saturday, March 10, 2012 at 11:18pm
here is how I do these ....
(perhaps you might find it easier in degrees, 19π/4 radians = 855°
sin(19π/4) = sin 855°
take away 2 rotations, (720° or 4π)
sin 19π/4 = sin 3π/4 = sin 135°
3π/4 or 135° is in quadrant II and π/4 or 45° from the x-axis
We also know that in II, the sine is positive
so sin 3π/4 = sin π/4 = sin 45° = 1/√2 or √2/2
d) cos(53π/4) or cos 2385°
take away 12π or 2160°
cos 53π/4 = cos 5π/4 or cos 225°
This angle is in quad III making it negative and 45 from the x-axis
cos 53π/4 = - cos π/4 = -1/√2 or -√2/2
do the others the same way.
Answer this Question
- Math - Evaluate *Note - We have to find the exact value of these. That I know to...
- Math integrals - What is the indefinite integral of ∫ [sin (π/x)]/ x^...
- Trig Help! - Question: Trying to find cos π/12, if cos π/6 = square ...
- Math, please help - Which of the following are trigonometric identities? (Can be...
- product of function - Given: f(x)=2 cos x and g(x)=sin x. Which of these ...
- Math 2nd question - Express as a single sine or cosine function (note: this is ...
- TRIGONOMETRY - Can you check my work, please? This is for a trig study guide for...
- Math help again - cos(3π/4+x) + sin (3π/4 -x) = 0 = cos(3π/4)cosx...
- Advanced Functions/Precalculus - 1. The expression sinπ is equal to 0, ...
- Math Help - Hi! Can someone help check this for me and see if I'm doing it right...