Posted by Hannah on Monday, May 6, 2013 at 10:10pm.
cos[(tan^1(3/4))+(cos^1(9/41))]

Trig  Reiny, Monday, May 6, 2013 at 10:42pm
let tan^1 (3/4) = A and let cos^1 (9/41) = B
then cos[(tan^1(3/4))+(cos^1(9/41))]
= cos(A + B)
= cosA cosB  sinA sinB
IF tan^1 (3/4) = A
then tanA = 3/4
> sinA = 3/5 and cosA = 4/5, recognize the 345 right angled triangle
if cos^1 (9/41) = B
then cosB = 9/41
> x^2 + y^2 = r^2
81 + y^2 = 1681
y^2 = 1600
y = √1600 = 40 and thus sinB = 40/41
so back to
cosA cosB  sinA sinB
= (4/5)(9/41)  (3/5)(40/41) = 84/205
( I tested my answer with my calculator, it is correct)
Answer This Question
Related Questions
 Trig  Given: cos u = 3/5; 0 < u < pi/2 cos v = 5/13; 3pi/2 < v < ...
 Trig.  sec^2xcotxcotx=tanx (1/cos)^2 times (1/tan)(1/tan)=tan (1/cos^2) times...
 trig  Show that 1cos2A/Cos^2*A = tan^2*A 1cos2A/Cos^2*A = [Cos^2(A)  Cos(2A...
 precalculus  For each of the following determine whether or not it is an ...
 trig 26  simplify to a constant or trig func. 1. sec ²utan ²u/cos ²v+sin ²v ...
 TRIG  what is another form of: sin (A+B) sin (AB)/ cos^2 A cos^2 B a) cos^2 A...
 Mathematics  Trigonometric Identities  Let y represent theta Prove: 1 + 1/tan^...
 TRIG!  Posted by hayden on Monday, February 23, 2009 at 4:05pm. sin^6 x + cos^6...
 Trigonometry desperate help, clueless girl here  2. solve cos 2x3sin x cos 2x=...
 Trigonometry  Please review and tell me if i did something wrong. Find the ...
More Related Questions