Monday

December 22, 2014

December 22, 2014

Posted by **Dee** on Monday, November 8, 2010 at 11:40pm.

sin a = 4/5, -3pi/2<a<-pi;

tan b = -sqrt2, pi/2<b<pi

identity used is:

tan(a-b)=(tan a-tan b)/1+tan a tan b

simplify answer using radicals.

(a is alpha, b is beta)

- Trigonometry -
**Reiny**, Monday, November 8, 2010 at 11:54pmBoth the sine and cosine curves are the same for

-3pi/2<a<-pi as they are for π/2<a<π (2nd quad)

so if sina = 4/5, then cosa = -3/5

and tana = -4/3

then tan(a-b)

= (tana - tanb)/(1 + tanatanb)

= ((-4/3) - (-√2))/( 1 + (-4/3)(-√2))

= (√2 - 4/3)/(1 + 4√2/3)

= (3√2 - 4)/(3 + 4√2)

I don't know if you have to rationalize that, if you do carefully multiply top and bottom by (3 - 4√2)

- Trigonometry -
**Dee**, Tuesday, November 9, 2010 at 12:16amI put that in but it said the answer was

36-252/23

any idea how that works?

- Trigonometry -
**Reiny**, Tuesday, November 9, 2010 at 12:40amThat is exactly what my answer works out to if you rationalize it.

I had suggested to do that.

**Answer this Question**

**Related Questions**

precalculus - For each of the following determine whether or not it is an ...

Math-Trigonometry - Show that if A, B, and C are the angles of an acute triangle...

Trig - Given: cos u = 3/5; 0 < u < pi/2 cos v = 5/13; 3pi/2 < v < ...

Trigonometry - 1.Solve tan^2x + tan x 1 = 0 for the principal value(s) to two ...

Integration - Intergrate sec^3(x) dx could anybody please check this answer. ...

Trig - tan 15 using composite argument? - tan 15 tan (45-30) (tan 45 - tan ...

Maths- complex numbers - Find tan(3 theta) in terms of tan theta Use the formula...

calculus - can anyone tell me if tan-1x= 1 over tan x? No. They are different. ...

Maths Calculus Derivatives - Find the first derivative for the following ...

Trigonometry desperate help, clueless girl here - 2. solve cos 2x-3sin x cos 2x...