Friday

February 27, 2015

February 27, 2015

Posted by **Lucy** on Saturday, August 30, 2008 at 10:12pm.

Find the value of tan(a-b) if cos a=-3/5, sin b=5/13, 90<a<180, and 90<b<180

Thanks for any help

- Pre-Calculus -
**Reiny**, Saturday, August 30, 2008 at 10:48pmyour text should have

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

so you will need tan a and tan b

cos a = -3/5 and a is in the second quadrant, so by sketching a diagram it is easy to see that sin a = 4/5 and

tan a = - 4/3

similarly sin b = 5/13 and b is in quadrant II, so cos b = -12/13 and

tan b = -5/12

then tan(a-b)

=(-4/3 - (5/12))/(1 + (-4/3)(-5/12))

= -33/56

**Answer this Question**

**Related Questions**

Pre calculus - How do you work this problem? Find the exact value of sin 2u, cos...

trig - I am very confused about the concepts of.. sin è = sin(180 - è) sin (180...

Trig - A. Find simpler, equivalent expressions for the following. Justify your ...

Trig - Can someone check my answers so far? 1. Find the exact value of tan(-3ð) ...

pre-calc helpppp - Find sin x/2, cos x/2, and tan x/2 from the given information...

pre-calculus - cosx= -8/17, 180<x<270 find; sin(x/2) cos(x/2) tan(x/2)

Pre-Calc Help!!! - Find sin x/2, cos x/2, and tan x/2 from the given information...

Trigonometry - Identities - If tan 2x = - 24/7, where 90 degrees < x < 180...

Maths - 1) Simplification (trigonometric ratios of allied angles)? Simplify : i...

Calculus - Find the exact values of the following. cos 270 degrees = 90 degrees...