Tuesday

July 22, 2014

July 22, 2014

Posted by **anoynomous** on Saturday, March 16, 2013 at 2:41pm.

tan-1 (1/7) + tan-1 (1/13) = tan-1(2/9)

- maths-trignometry -
**Reiny**, Saturday, March 16, 2013 at 3:02pmlet tanA = 1/7 and tanB = 1/13

then tan(A+B) = (tanA + tanB)/( 1 - tanAtanB)

= (1/7 + 1/13)/(1 - (1/7)(1/13) )

= (20/91) / (90/91) = 20/90 = 2/9

and if we let tanC = 2/9

then A + B = C

thus tan^-1 (1/7) + tan^-1 (1/13) = tan^-1 (2/9)

check with your calculator

take 2nd Tan (1/7) = 8.13010..

take 2nd Tan(1/13) = 4.39871

add them: 12.5288..

take 2nd Tan(2/9) = 12.5288..

**Related Questions**

Trigonometry - Find the exact value of tan(a-b) sin a = 4/5, -3pi/2<a<-pi...

trignometry - Tan4x=4tanx(1-tan^x)/1-6tan^x+tan^^x ,prove

trignometry - 1. if sin 2A = Psin2B, prove that tan(A+B)/tan(A-B)=P+1/P-1.

Trigonometry desperate help, clueless girl here - 2. solve cos 2x-3sin x cos 2x...

precalculus - For each of the following determine whether or not it is an ...

Trigonometry - 1.Solve tan^2x + tan x – 1 = 0 for the principal value(s) to two ...

Trig - tan 15° using composite argument? - tan 15° tan (45°-30°) (tan 45° - tan ...

Math-Trigonometry - Show that if A, B, and C are the angles of an acute triangle...

Trig. - sec^2xcotx-cotx=tanx (1/cos)^2 times (1/tan)-(1/tan)=tan (1/cos^2) times...

Maths Calculus Derivatives - Find the first derivative for the following ...