Solving Acute Triangle Angles Given $A,B,C$ & Equations

In summary, an acute triangle is a triangle with all three angles measuring less than 90 degrees. To solve for the angles of an acute triangle, you can use the law of sines or the law of cosines. However, an acute triangle cannot have two equal angles. If the given equations do not produce valid angles, it means the measurements do not form an acute triangle. Special cases to be aware of when solving for the angles of an acute triangle include right triangles and equilateral triangles.
  • #1
maxkor
84
0
Given that $A,B,C$ be angles in an acute triangle.

If $(5+4\cos A)(5-4\cos B)=9$ and $(13-12\cos B)(13-12\cos C)=25$

find $cos(A+C)$.
I know $A+B+C=180^{o}$ and $\cos B=-\cos(A+C)$ and what next?
 
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  • #2
Hi, maxkor!(Wave)

Thankyou for sharing your problem on the MHB site!

You ask for the next step. One way (which worked for me) would be to isolate $\cos B$ in both equations.

I suggest, you try this out(Nod)
 

What is the definition of an acute triangle?

An acute triangle is a triangle in which all three angles measure less than 90 degrees.

How do you solve for the angles of an acute triangle given $A, B, C$ and equations?

To solve for the angles of an acute triangle, you can use the law of sines or the law of cosines. First, determine which angles you are given and which angles you need to solve for. Then, use the appropriate equation and solve for the missing angle.

Can an acute triangle have two equal angles?

No, an acute triangle cannot have two equal angles. Since all three angles are less than 90 degrees, they must all be unique.

What happens if the given equations do not produce valid angles for an acute triangle?

If the given equations do not produce valid angles for an acute triangle, it means that the given measurements do not form an acute triangle. This could be due to measurement errors or an incorrect triangle type assumption.

Are there any special cases when solving for the angles of an acute triangle?

Yes, there are a few special cases to be aware of when solving for the angles of an acute triangle. These include when the given measurements form a right triangle (one angle measures exactly 90 degrees) or an equilateral triangle (all three angles measure exactly 60 degrees).

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