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In a triangle ABC, a = 4, b = 3, ∠BAC = 60°, then the education for which c is the root, is
c2−3c−7=0
Explanation
Concept:
Cosine formula or cosine rule
∙ a2=b2+c2−2bccosA⇒cosA=2bcb2+c2−a2
∙ b2=a2+c2−2accosB
∙ c2=a2+b2−2abcosC
Calculation:
Given: a = 4, b = 3, ∠BAC = 60°
Using cosine formula, we get
cosA=2bcb2+c2−a2
⇒ cos 60° = \frac{3^2 + c^2 - 4^2}{2 \times 3 \times c}
⇒ 21×6c=9+c2−16
⇒ c2−3c−7=0
Explanation
Concept:
Cosine formula or cosine rule
∙ a2=b2+c2−2bccosA⇒cosA=2bcb2+c2−a2
∙ b2=a2+c2−2accosB
∙ c2=a2+b2−2abcosC
Calculation:
Given: a = 4, b = 3, ∠BAC = 60°
Using cosine formula, we get
cosA=2bcb2+c2−a2
⇒ cos 60° = \frac{3^2 + c^2 - 4^2}{2 \times 3 \times c}
⇒ 21×6c=9+c2−16
⇒ c2−3c−7=0
