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The sides of an isosceles triangle are 5, 5, and 7. Find the measure of the vertex angle to the nearest degree.
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May 5, 2017
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The sides of an isosceles triangle are 5, 5, and 7. Find the measure of the vertex angle to the nearest degree.
Mathematics
high-school
Cyrcle
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Cyrcle
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You can use the cosine law with the formula:
a^2 = b^2 + c^2 - 2*b*c*cosA
With a = 5, b = 5, c = 7,
7^2 = 5^2 + 5^2 - 2*5*7*cosA
49 = 25 + 25 - 70*cosA
70*cosA = 25 + 25 - 49
70*cosA = 1
cosA = 1/70
A = arccos (1/70) = 89.18 deg = 89 deg
RnMss
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May 9, 2017
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