Given cos A = .25 find angle A in degrees. Round your answer to the nearest hundredth.
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Answer:
Step-by-step explanation:
For a triangle the area is
If our triangle is isosceles and the 2 congruent sides each measure 4 and they include an angle of 40 degrees, let's say that the vertex angle is 40 and the sides that are not the base each measure 4. If we drop an altitude from the vertex to the base, we cut the triangle into 2 right triangles, with the vertex angle being 20 degrees and the hypotenuse being 4. To find the base, then, which is opposite the angle, we use the sin ratio:
and
4sin(20) = b so
b = 1.368
But we need the whole base, and that is only half of it. So
2b = 2.736
To find the height, which is adjacent to the angle, we use the cos ratio:
and
4cos(20) = h so
h = 3.759
Now we have enough info to find the area of the triangle using the triangle area formula from above:
and
A = 5 meters squared.