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For positive acute angles A and B, it is known that sin A = 8/17 and cos B = 24/25
Find the value of sin(A + B) in simplest form.

Sagot :

Altavistardidn

Answer:

Step-by-step explanation:

Here we use the SUM FORMULA:  sin(a + b) = sin a cos b + cos a sin b

sin(A + B) = sin A*cos B + cos A*sin B.  We are not given cos A or sin B and so must find them using the Pythagorean Theorem x^2 + y^2 = z^2.

Looking at sin A = 8/17, we see that the "opposite side" is 8 and the "hypotenuse" is 17.  Then (adjacent side) = √(17² - 8²) = 15; that is, the side adjacent to Angle A is 15.  Thus, cos A = 15/17 and sin A = 8/17.

We find sin B similarly.  cos B = (side adjacent to B)/25  =  24/25.  Therefore the side opposite B is √(25² - 24²) = 7.  Thus, sin B = 7/25 and cos B = 24/25.

Then sin (A + B) = sin A*cos B + cos A*sin B

                           = (8/17)*(24/25) + (15/17)(7/25)

Here there are two products of fractions.  This product (above) can be rewritten as

                                                    8(24) + 15(7)             (3)(64) + (3)(5)(7)

= sin A*cos B + cos A*sin B = --------------------------- = --------------------------

                                                            17(25)                         17(25)

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