Monday

July 28, 2014

July 28, 2014

Posted by **mysterychicken** on Wednesday, January 30, 2013 at 6:10pm.

Please help! Thanks

- Math -
**Reiny**, Wednesday, January 30, 2013 at 6:44pmcosx = 4/5 and x is in quad IV

So sinx = - 3/5

sin 2x = 2sinxcosx

= 2(-3/5)(4/5) = -24/25

- Math -
**mysterychicken**, Wednesday, January 30, 2013 at 6:57pmif tan x = -7/24 and 3π/2 < x <2π find cot x/2

Thanks so much!

- Math -
**Reiny**, Wednesday, January 30, 2013 at 7:31pmDon't post a new question in the thread of a question.

Tutors will see a reply and ignore it

Start a new entry.

if tanx = -7/24 and x is in IV

then sin x = -7/25 and cosx = 24/25

cot x/2

= cos x/2 / sin x/2

recall cos 2A = 2cos^2 A - 1 or 1 - 2sin^2 A

cos x = 2cos^ x/2 - 1

24/25 + 1 = 2cos^2 x/2 = 49/25

cos^2 x/2 = 49/50

cos x/2 = -7/(5√2) , if x is in IV , then x/2 is in II , therefore negative

cos x = 1 - 2sin^2 x/2

24/25 - 1 = -2sin^2 x/2 = -1/25

sin^2 x/2 = 1/50

sin x/2 = +1/(5√2)

cot x/2 = cos x/2 / sin x/2

= -7/(5√2) / 1/(5√2) = -7

- Math -
**mysterychicken**, Wednesday, January 30, 2013 at 8:14pmThank you soo much!

**Related Questions**

MATH - 1.)Find the exact solution algebriacally, if possible: (PLEASE SHOW ALL ...

Algebra II - Multiple Choice (theta) means the symbol 0 with the dash in it. 1.)...

Trigonometry - use the appropriate trig identity (sum and difference, half angle...

TRIG/ALGEBRA - 1) Find the exact value. Use a sum or difference identity. tan (-...

trigonometry (please double check this) - Solve the following trig equations. ...

Trig - find cos x/2, sin x = 1/4, 360 < x < 450, use half-angle identity

precalculus - write each expression as the sine, cosine or tangent of a double ...

Trig - If cosx = 10/19 an pi < x < 2pi, find the exact value of cos x/2 ...

Trig - Half angle identities Find exact values of a) cos 1/2 b) sin 1/2 c) tan 1...

MathsSs triG - Consider sin(x-360)sin(90-x)tan(-x)/cos(90+x) 1.A.SIMPLIFY sin(x-...