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Math Homework Help-Pythagorean triple?
Pythagorean Triple-
If a triangle is 4 5 7 is it acute, obtuse or right?
2 Answers
- Anonymous1 decade agoFavorite Answer
By law of cosines α² = ß² + c² - 2ßccos(A):
4² = 5² + 7² - 2(5)(7)cos(A)
16 = 25 + 49 - 70cos(A)
16 = 74 - 70cos(A)
-58 = -70cos(A)
cos(A) = 58/70
A = arccos(58/70)
Do the same for other angles, and we have <B ≈ 44.4°. You can tell that a triangle is obtuse since <A + <B < 90°
I hope this helps!
Source(s): Knowledge - 1 decade ago
to find the angles use The law of cosines
cos A= (b²+c² -a²)/2bc
cos B= (a²+c² -b²)/2ac
a=4, b=5, c=7
cosA= (25+49-16)/2*5*7=58/70
<A= 34 degrees
cosB=16+49-25)/2*4*7=40/56
<B=44.4 degrees
Sum of interior angles of a triangle =180 degrees
<C+180 -44.4 -34
