Trigonometry

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r267747

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Oct 1, 2009
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Tomorrow is my exam so please solve these questions immediately
1. If cos(A-B)+cos(B-C)+cos(C-A)=-3/2
Prove that
cosA+cosB+cosC=sinA+sinB+sinC=0
2. If A+B=PI/4, PROVE THAT:
(1+tanA) (1+tanB)=2tanA
I know that the formula is tan(A+B)=(tanA+tanB)/1-tanAtanB but I do not know how to use it in this question
3.PROVE THAT:
i) tan69+tan66+1=tan69tan66
ii)(cos13+sin13)/cos 13-sin13=tan58
please tell me which one formala I will apply in both these parts
 
r267747 said:
Tomorrow is my exam so please solve these questions immediately
1. If cos(A-B)+cos(B-C)+cos(C-A)=-3/2
Prove that
cosA+cosB+cosC=sinA+sinB+sinC=0
2. If A+B=PI/4, PROVE THAT:
(1+tanA) (1+tanB)=2tanA
I know that the formula is tan(A+B)=(tanA+tanB)/1-tanAtanB but I do not know how to use it in this question
3.PROVE THAT:
i) tan69+tan66+1=tan69tan66
ii)(cos13+sin13)/cos 13-sin13=tan58
please tell me which one formala I will apply in both these parts
Click to expand...
 
r267747 said:
Tomorrow is my exam so please solve these questions immediately
1. If cos(A-B)+cos(B-C)+cos(C-A)=-3/2
Prove that
cosA+cosB+cosC=sinA+sinB+sinC=0
2. If A+B=PI/4, PROVE THAT:
(1+tanA) (1+tanB)=2tanA
I know that the formula is tan(A+B)=(tanA+tanB)/1-tanAtanB but I do not know how to use it in this question
3.PROVE THAT:
i) tan69+tan66+1=tan69tan66
ii)(cos13+sin13)/cos 13-sin13=tan58
please tell me which one formala I will apply in both these parts
Click to expand...
 
r267747 said:
r267747 said:
Tomorrow is my exam so please solve these questions immediately
1. If cos(A-B)+cos(B-C)+cos(C-A)=-3/2
Prove that
cosA+cosB+cosC=sinA+sinB+sinC=0

What part of the solution I presented - you failed to understand?

2. If A+B=PI/4, PROVE THAT:
(1+tanA) (1+tanB)=2tanA

This is not the same problem you had posted before - please check the "signs" (+ or -) for accuracy

I know that the formula is tan(A+B)=(tanA+tanB)/1-tanAtanB but I do not know how to use it in this question
3.PROVE THAT:
i) tan69+tan66+1=tan69tan66
ii)(cos13+sin13)/cos 13-sin13=tan58
please tell me which one formala I will apply in both these parts
Click to expand...
Click to expand...
 
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