Posted by **shreya** on Monday, May 30, 2011 at 6:24am.

if sinA+cosA=1/5, then a value of tanA/2 satisfies which of the equation?

a. 2x^2-x-1

b.x^2-2x-3=0

c.2x^2-5x-3=0

d. 2x^3-7x^2+2x+3=0

- maths -
**Reiny**, Monday, May 30, 2011 at 8:45am
sinA+cosA=1/5

square both sides

sin^2A + 2sinAcosA + cos^2A = 1/25

2sinAcosA = 1/25 - 1 = -24/25

sin 2A = -24/25

setting my calculator to radians

2A = 4.4286 or 2A = 4.9962

A/2 = 1.10715 or A/2 = 1.249

so tan A/2 = 3.99999 or tan A/2 = 3

or tan A/2 = 0

clearly 0 does not work as a zero for any of the given equations, (they all have a constant)

tan A/2 = 3 does work in equation b)

which would factor to (x-3)(x+1) = 0 to get a root of 3

3 is also a root of c) and d) since they both factor containing a factor of (x-3)

( I know I should have been able to get tan A/2 = 3 without relying on my calculator,

## Answer This Question

## Related Questions

- Maths - Hi, can someone give me the answer to this question: secA-tanA=1/4. Find...
- maths(trigonometry) - prove that sinA-cosA+1/sinA+cosA-1=1/secA-tanA
- trig - Establish the following identity: CosA/1-TanA + SinA/1-CotA = CosA-SinA
- further mathematics - Let P=(cosA sinA) (sinA cosA) Q=(cosB sinA) (sinB cosA) ...
- trig - if 5cos A plus 3=0 and 180<A<360..without using a calculator and ...
- Trigonometry - If sinA + sinB = a and cosA + cosB = b, find the value of tanA-B/...
- Maths, Divine International Public School - If 15Cot=8, find (1+SinA)(1-SinA)/(1...
- mathematics trignometry - prove that the following are identity 1. (cotA+cosecA-...
- MathS triG - 1 .If tanA=1/3 and tanB=1/7 (both A and B are acute),calculate ...
- maths Pls help trig - 1 .If tanA=1/3 and tanB=1/7 (both A and B are acute),...

More Related Questions