In the triangle ABC, if a: B: C = 7:8:13, then the cosine of the largest inner angle in the triangle is
cosC=(7^2+8^2-13^2)/(2X7X8)=-1/2
RELATED INFORMATIONS
- 1. In △ ABC, if C = 60 ° and C2 = AB, then the shape of triangle is () A. Right triangle B. isosceles triangle C. equilateral triangle D. obtuse triangle
- 2. It is known that the three sides a, B and C of △ ABC satisfy A2 + B2 + C2 = 10A + 24B + 26c-338. Please judge the shape of △ ABC and explain the reason
- 3. In △ ABC, if B = 60 °, B & # 178; = AC, then C=
- 4. In △ ABC, B & # 178; = AC, B = 60 °, then a
- 5. In ABC, we know that B & # 178; - C & # 178; = A & # 178; + AC, then B =? A. 45 ° B, 120 ° C, 30 ° or 150 ° D, 60 ° or 120 ° C
- 6. As shown in the figure, in the triangle ABC, the angle a is equal to 60 degrees It is known that, as shown in the figure, in the triangle ABC, the angles a are equal to 60 degrees CE and BF are bisectors of the triangle ABC angles and intersect at point D Prove that De is equal to DF
- 7. Given that the opposite sides of the inner angles a, B and C in the acute angle △ ABC are a, B and C respectively, and a & # 178; + B & # 178; = C & # 178; + AB, find the value of angle C,
- 8. It is known that the opposite sides of the internal angles a, B and C of triangle ABC are a, B and C respectively. If a & # 178; + B & # 178; - C & # 178; + AB = 0, then the size of angle c is?
- 9. If the three sides of △ ABC are a, B, C, and its area is ᦉ 188; (a ᦉ 178; + B ᦉ 178; - C ᦉ 178;), then what is the internal angle c?
- 10. If the area of △ ABC is s = a # 178; - (B-C) # 178;, then Tan (A / 2)= A1/2 B1/4 C1/8 D1
- 11. In △ ABC, if a = 7, B = 8, COSC = 1314, then the cosine of the largest angle is () A. −15B. −16C. −17D. −18
- 12. In the triangle ABC, the cosine of ∠ A is 5 / 13, and the cosine of ∠ B is 4 / 5?
- 13. In △ ABC, if a = 7, B = 8, COSC = 1314, then the cosine of the largest angle is () A. −15B. −16C. −17D. −18
- 14. Finding cosine C in triangle ABC with a = 3, B = 5 and C = 7
- 15. In △ ABC, if Sina: SINB: sinc = 2:3:4, then the cosine value of the largest angle=______ .
- 16. In △ ABC, if sin B = 2sinacosc and the cosine of the minimum angle is 3 / 4, (1) judge the shape of triangle ABC, (2) find the maximum angle of ABC
- 17. In △ ABC, the points o and E are on AB and AC respectively, ∠ DCB = ∠ EBC = 1,2 ∠ a, be and CD intersect at point O to prove BD = CE The following first answer is not for junior high school students, the second answer is wrong, also can't be used, hope someone continue to give guidance.
- 18. Known: as shown in the figure, in △ ABC, if ∠ A is an acute angle, points D and E are on AB and AC respectively, and ∠ DCB = ∠ EBC = 12 ∠ A. verification: BD = CE
- 19. Known: as shown in the figure, in △ ABC, if ∠ A is an acute angle, points D and E are on AB and AC respectively, and ∠ DCB = ∠ EBC = 12 ∠ A. verification: BD = CE
- 20. In the triangle ABC, the points D and E are on AB and AC, and the angle EBC = angle DCB = I / 2 angle a, BD = CE is proved