Saturday

January 31, 2015

January 31, 2015

Posted by **House** on Friday, October 3, 2008 at 1:16pm.

tan(a) = -1/2

oppsite side = 1: adjacentside = 2

hypotenuse = sqrt(1+4) = sqrt(5)

sin(a) = 1/5

cos(a) = -2/5

tan(b) = -2/3

opposite side = 2 and adjacentside = 3

hypotenuse = sqrt(4+9) = 13

sin(b) = 2/13

cos(b) = -3/13

cos(a+b) = cosa cosb - sina sinb

=(-2/5)(-3/13) - (1/5)(2/13)

= 6/65 - 2/65

= 4/65

right?

- Math -
**bobpursley**, Friday, October 3, 2008 at 1:58pmI didn't check all, but you have the technique. You can easily check these on your calculator.

**Answer this Question**

**Related Questions**

Math - If α and β are two angles in Quadrant II such that tan α...

Trig. - sec^2xcotx-cotx=tanx (1/cos)^2 times (1/tan)-(1/tan)=tan (1/cos^2) times...

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

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

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

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

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

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

Trigonometry - Find the exact value of tan(a-b) sin a = 4/5, -3pi/2<a<-pi...

math - Use the exact values of the sin, cos and tan of pi/3 and pi/6, and the ...