prove that cos(A+B) =cosA.cosB-sinA.sinB
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the distance of point (2,3,4) from the x-axis.
3. If a+b+c=0 and IaI=3, IbI=5 andIcI=7, show that the angle between a and b is 60 degree.
4. Find a vector r of magnitude 3 root 2 units which makes an angle of pi by 4 and pi by 2 with y and z axes respectively.
5. Using vectors, prove that cos(A-B)=cosA cosB+ sinA sinB.
6. Prove that in a triangle ABC, sinA/a=sinB/b=sinC/c, where a,b,c represent the magnitude of the sidesopposite to vertices A,B,C respectively.
3. If a+b+c=0 and IaI=3, IbI=5 andIcI=7, show that the angle between a and b is 60 degree.
4. Find a vector r of magnitude 3 root 2 units which makes an angle of pi by 4 and pi by 2 with y and z axes respectively.
5. Using vectors, prove that cos(A-B)=cosA cosB+ sinA sinB.
6. Prove that in a triangle ABC, sinA/a=sinB/b=sinC/c, where a,b,c represent the magnitude of the sidesopposite to vertices A,B,C respectively.
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