
New Member
Addition and Subtraction Formula Trig: evaluate sin(255),
I'm having trouble on these problems and their due tonight, its the only problems I have left on my homework if anyone can help on any of them it will be much appreciated.
Find the area of a triangle that has the following dimensions. Give your answer correct to the tenth place.
sides of length 6 and 9, and included angle 76°.
Use an addition or subtraction formula to find the exact value of the expression.
Sin (255)
Tan (195)
Tan (5pie/12)
cos (80) cos (10)  sin (80) sin (10)
I keep getting 0 and 1 for this problem but its wrong.
cos (7pie/6) cos (pie/2) sin (7pie/6) sin (pie/2)

Full Member
Re: Addition and Subtraction Formula Trig
Perhaps you should start with the cosine law with the triangle.
255=360(60+45)
195 = 180+15
[tex]5\pi/12 = \pi/4+\pi/6[/tex]
90=80+10
2/3 = 7/6  1/2

Senior Member
Re: Addition and Subtraction Formula Trig
After using the Law of Cosines to find the length of the third side, use Hero's formula for its area.
sin 255° = sin(30045)
tan(195) = tan (15045)
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