Author Topic: Quick question (Read 719 times) Tweet Share

darkphoenix · « **on:** February 28, 2010, 10:33:29 pm »

Hey just a quick question:

Need to solve tan 75 degrees using a compound angle formula in simplest surd form.

Thanks.

olly_s15 · « **Reply #1 on:** February 28, 2010, 10:41:40 pm »

Should this be in the methods section?

Anyway, just use tan45 and tan30 plug into compound tan formula?

darkphoenix · « **Reply #2 on:** February 28, 2010, 10:48:58 pm »

Yeah its part of methods.

And thats what i did, but i got some weird answer, different to textbook.

olly_s15 · « **Reply #3 on:** February 28, 2010, 10:51:05 pm »

double check on calculator then.. and i'm quite sure compound angle formulas isn't part of the methods course?

darkphoenix · « **Reply #4 on:** February 28, 2010, 10:58:34 pm »

Quote from: olly_s15 on February 28, 2010, 10:51:05 pm

double check on calculator then.. and i'm quite sure compound angle formulas isn't part of the methods course?

Thats weird? Its part of trig (circular functions).

Yeah problem is the calc doesnt show working.

QuantumJG · « **Reply #5 on:** February 28, 2010, 11:05:54 pm »

Just use the compound formula for tan:

$tan(75^{o}) = tan(45^{o} + 30^{o}) = \dfrac{tan(45^{o}) + tan(30^{o})}{1 - tan(45^{o})tan(30^{o})}$

$= \dfrac{1 + \dfrac{ \sqrt{3} }{3} }{1- \dfrac{ \sqrt{3} }{3} }$

$= \dfrac{3 + \sqrt{3} }{3 - \sqrt{3} }$

$= \dfrac{3 + \sqrt{3} }{3 - \sqrt{3} } \times \dfrac{3 + \sqrt{3} }{3 + \sqrt{3} }$

$= 2 + \sqrt{3}$

darkphoenix · « **Reply #6 on:** February 28, 2010, 11:19:11 pm »

Oh just realised i wrote the formula down wrong. =.=

No wonder i got some retarded answer.

Cheers dude.

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