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Algebra II/ Trig help?
find the exact values of sin u/2 sos u/2 and tan u/2
cos u = 4/5 3pi/2 < u < 2pi
i will get it if you show the steps, i just don't have a text book
sorry for not being more specific, we are useing double and half angle formulas in our current lesson and i cant remember how to use them those for that type of problem.
2 Answers
- LE THANH TAMLv 51 decade agoFavorite Answer
3pi / 2 < u < 2pi , in quadrant I V , x > 0 , y < 0 , sin u / 2 < 0
tan u / 2 < 0
so
sin u / 2 = - sqrt [ ( 1 - cos u ) / 2 ]
sin u / 2 = - sqrt { [ 1 - ( 4 / 5)] / 2 }
sin u / 2 = - sqrt ( 1 / 10)
sin u / 2 = - [ sqrt ( 10 )] / 10
tan u / 2 = - sqrt [ ( 1 - cos u) / ( 1 + cos u )]
tan u / 2 = - sqrt { [ 1 - ( 4 / 5)] / [ 1 + ( 4 / 5)] }
tan u / 2 = - sqrt ( 1 / 9)
tan u / 2 = - 1 / 3
- 1 decade ago
cosU = 4/5
then..
sinU = 3/5
tanU = 3/4
draw the triangle.. SOH CAH TOA..
cos is adjacent over hypotenuse
use the pythagorean theorem to find the other leg..
