Sunday

March 1, 2015

March 1, 2015

Posted by **Jenny** on Saturday, June 19, 2010 at 5:10am.

find the exact value of tan2A

- Maths 3u trig -
**Damon**, Saturday, June 19, 2010 at 6:35amsinA = 1/3 and cosA<0

find the exact value of tan2A

What quadrant is A? Sin is +, cos is - so quadrant 2, so 2 A is quadrant 3 or 4

cos^2A = 1 - sin^2A = 1-1/9 = 8/9

cos A = -(2/3)sqrt 2

tanA = (1/3)/[-(2/3)sqrt2)] = -1/(2 sqrt 2)

tan 2A = 2 [-1/(2 sqrt 2)]/[1- 1/8]

**Answer this Question**

**Related Questions**

Maths - Hi, can someone give me the answer to this question: secA-tanA=1/4. Find...

further mathematics - Let P=(cosA sinA) (sinA cosA) Q=(cosB sinA) (sinB cosA) ...

Maths, Divine International Public School - If 15Cot=8, find (1+SinA)(1-SinA)/(1...

trig - Please help me how to do this: 1) 1 + sina*cosa / (cosa + sina)^2 = 2) ...

trig - Establish the following identity: CosA/1-TanA + SinA/1-CotA = CosA-SinA

trig - prove that :cosA-sinA+1/cosA+sinA-1=cosecA+cotA

maths(trigonometry) - prove that sinA-cosA+1/sinA+cosA-1=1/secA-tanA

trig - I need to count this: a) 1-tg^2a/1+ctg^2a, when sina =2/3 b) 1-tg^2a/1-...

trig - Prove : (sinA-cosA+1)/(sinA+cosA-1) = (1+sinA)/cosA

trig - if 5cos A plus 3=0 and 180<A<360..without using a calculator and ...