Posted by **manda** on Tuesday, April 10, 2007 at 10:24pm.

if sinx=(4/5), where 0 degrees<x<90 degrees, find the value of cos (x+180)

25+25+100+n=250

since x is in the first quadrant, then x+180º is in the third quadrant, and cos(x+180) = =cos x

You should recognize the 3,4,5 right-angled triangle and cosx = 3/5

so cos(x+180)=-3/5

3x+y=90+2x+y=90

## Answer This Question

## Related Questions

- math - how to define arc cosine(cosine x) for -360 deg<x< 360 deg?? a ...
- Calculus - Find the exact values of the following. cos 270 degrees = 90 degrees...
- trig help - I need help finding sinA if cosA=(-3/5) and A is greater than 90 ...
- Trig - A. Find simpler, equivalent expressions for the following. Justify your ...
- trig - I am very confused about the concepts of.. sin è = sin(180 - è) sin (180...
- basic geometric - a would like to get someone too help me with these math ...
- Algebra II - Multiple Choice (theta) means the symbol 0 with the dash in it. 1.)...
- Pre Calc. - Use the sum or difference identity to find the exact value of sin255...
- Trig (Last URGENT) - sin2x+cosx=0 , [-180,180) = 2sinxcosx+cosx=0 = cosx(2sinx+1...
- physics - A) Assume the mass of a pendulum is 3kg. Calculate the work done by ...

More Related Questions