1. ## cos,sin,tan

Given that cos A= 3/2 cosB= 24/25 where A and B are acute find the exact values of

a) tan A

b) sin B

c) cos (A-B)

d) tan(A+B)

could any show me how these questions are solved?

Thank you.

2. Originally Posted by Oasis1993
Given that cos A= 3/2 cosB= 24/25 where A and B are acute find the exact values of

a) tan A

b) sin B

c) cos (A-B)

d) tan(A+B)

could any show me how these questions are solved?

Thank you.
Hi oasis1993,

The range of y=cos A is [-1, 1].

$\cos A=\frac{3}{2}$ is out of range.

3. I dont understand how that is supposed to help me..?

4. Since the given cosine equation is not possible, then there is no solution to this exercise.

5. Originally Posted by Oasis1993
I dont understand how that is supposed to help me..?
Oasis1993,

Check to see if you copied the first cosine value correctly. Cosine A cannot be greater than 1 or less than -1. You have it as 3/2, which is greater than 1.

6. The question says 3/5.
I know we are supposed to use the identities and addition formulae's...but i dont really know how.

7. Originally Posted by Oasis1993
Given that cos A= 3/5 cosB= 24/25 where A and B are acute find the exact values of

a) tan A

b) sin B

c) cos (A-B)

d) tan(A+B)

could any show me how these questions are solved?

Thank you.
Originally Posted by Oasis1993
The question says 3/5.
I know we are supposed to use the identities and addition formulae's...but i dont really know how.
Ok, Oasis1993, that helps.

Since Cos A = 3/5, this means that x = 3 and r = 5. Solve for y in the following equation:

$r^2=x^2+y^2$

(a) $\tan A = \frac{y}{x}$

Since Cos B = 24/25, this means that x = 24 and r = 25. Solve for y in the following equation:

$r^2=x^2+y^2$

(b) $\sin B = \frac{y}{r}$

For (c) and (d), use your sum-difference formulas using the information you are given and the information you found.