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TRIGONOMETRY
- Thread starter r267747
- Start date
D
Deleted member 4993
Guest
r267747 said:PLEASE SOLVE THESE QUESTIONS;
1. if cos(A-B)+cos(B-C)+cos(C-A)=-3/2
Prove that;
cosA+cosB+cosC=sinA+sinB+sinC=0
Use
cos(X) + Cos(Y) = 2 * cos[(X+Y)/2] * cos[(X-Y)/2]
2. if A-B=pi/4,prove that;
a) (1+tanA) (1-tanB)=2
b)(1+tanA) (1+tanB)=2tanA
use:
tan (A+B) = [tan(A) + tan(B)]/[1 + tan(A)*tan(B)]
Please share with us your work, indicating exactly where you are stuck - so that we know where to begin to help you.
r267747 said:PLEASE SOLVE THESE QUESTIONS;
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;
a) (1+tanA) (1-tanB)=2
b)(1+tanA) (1+tanB)=2tanA
MY WORK
Sol1.:-cosA+cosB+cosC=sinA+sinB+sinC=0
2cos(A/2+B/2)cos(A/2-B/2)+cosC
I am confused here so please help me to solve this question
Sol2:- a)I have solved it
b)I know that the formula is same but I am unable to solve it
D
Deleted member 4993
Guest
r267747 said:r267747 said:PLEASE SOLVE THESE QUESTIONS;
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;
a) (1+tanA) (1-tanB)=2
b)(1+tanA) (1+tanB)=2tanA
MY WORK
Sol1.:-cosA+cosB+cosC=sinA+sinB+sinC=0
2cos(A/2+B/2)cos(A/2-B/2)+cosC
I am confused here so please help me to solve this question
Start from the given:
cos(A-B)+cos(B-C) + cos(C-A) = -3/2
cos(A-B)+cos(B-C) + cos(C-A)
= 2 * cos[(A-C)/2] * cos[(C+A)/2 - B] + 2cos[sup:3hydksw7]2[/sup:3hydksw7][(C-A)/2] - 1
Now see what do you get
Sol2:- a)I have solved it
b)I know that the formula is same but I am unable to solve it
Subhotosh Khan said:r267747 said:r267747 said:PLEASE SOLVE THESE QUESTIONS;
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;
a) (1+tanA) (1-tanB)=2
b)(1+tanA) (1+tanB)=2tanA
MY WORK
Sol1.:-cosA+cosB+cosC=sinA+sinB+sinC=0
2cos(A/2+B/2)cos(A/2-B/2)+cosC
I am confused here so please help me to solve this question
Start from the given:
cos(A-B)+cos(B-C) + cos(C-A) = -3/2
cos(A-B)+cos(B-C) + cos(C-A)
= 2 * cos[(A-C)/2] * cos[(C+A)/2 - B] + 2cos[sup:m0zx4aog]2[/sup:m0zx4aog][(C-A)/2] - 1
Please solve this question completely
Now see what do you get
Sol2:- a)I have solved it
b)I know that the formula is same but I am unable to solve it