In a triangle, knowing the sine or cosine of two angles, how to find the length of the opposite side and the sine (cosine) of the other angle?

In a triangle, knowing the sine or cosine of two angles, how to find the length of the opposite side and the sine (cosine) of the other angle?

If we know Sina and SINB, then sinc = sin (180-a-b) = - sin (a + b) = - sin acosb sinbcosa, so we know that sine can't determine the positive and negative cosine. It's OK to know cosine, because sine in triangle is positive
If you want to know the length of the corresponding edge, you must know a boundary value, and then calculate the length of the other two sides by the sine theorem a / Sina = B / SINB = C / sinc

Similarities and differences of measuring electric power of resistance by voltammetry

The same: 1, the same circuit 2, the same measured value 3, sliding rheostat has the role of protecting the circuit different: 1, sliding rheostat main role of different resistance, the role of sliding rheostat is to change part of the circuit current and voltage at both ends (that is, through the resistance of the current and voltage at both ends of the resistance) so that you can multiple measurements

In △ ABC, a ^ 2 + C ^ 2 = 2B ^ 2, where a, B and C are the side lengths of the angle ABC, (1) prove B ≤ 60 ° (2) if B = 45 ° and a is an obtuse angle, find a
If B = 45 ° and a is an obtuse angle, how to find a

(1) CoSb = (a ^ 2 + C ^ 2-B ^ 2) / 2Ac = (a ^ 2 + C ^ 2) / 4ac > = 2Ac / 4ac = 1 / 2 = > Ba ^ 2 + C ^ 2 = 2Ac * radical 2 and a is an obtuse angle
=>a> C = > A = (radical 2 + 1) C
A ^ 2 + C ^ 2 = 2B ^ 2 = > the relationship between B and C. by substituting the cosine theorem formula, cosa can be obtained

In the experiment of measuring the electric power of small bulb
When the actual voltage is 0.2 higher than the rated voltage of the small bulb, the ratio of the actual power of the small bulb to the rated power of the small bulb is
Hope to write the process

P real: P amount = u real ^ 2 / R: u amount ^ 2 / R (assume that the resistance of the filament is constant here)
So:
P real: P amount = u real ^ 2: u amount ^ 2 = 1.2 ^ 2:1
therefore
P real / P amount = 1.44/1

In △ ABC, ∠ C = 90 ° if Tana = 12, then Sina=______ ．

Let a = x, then B = 2x, then C = x2 + (2x) 2 = 5x, then Sina = AC = x5x = 55

Experiment of measuring electric power of small bulb
The rated voltage of the bulb is 3.8V, the filament resistance is about 8 Ω, and the power supply is three dry batteries
If the light bulb is only marked with 0.2A, how can they judge whether the light bulb is emitting normally?

The voltage and current marked on the electrical equipment are rated. 0.2A means that the rated current is 0.2 A. that is to say, only when the current passing through the bulb is 0.2A, it can be regarded as normal lighting, and its service life will not be affected. If the current is less than 0.2A, it can not reach the rated power, and it can emit light. It does not play the role of the bulb. If it is greater than 0.2A, it is easy to damage if it exceeds the rated power

The three sides a, B, C of triangle ABC are known, and | A-B | = 2a-a2-c2 is satisfied
A2 is the square of a, C2 is the square of C

a. B and C are positive real numbers,
|A-B | = 2a-a ^ 2-C ^ 2 > = 2a-2ac = 2A (1-C) > = 0, C = 0, a (2-A) > = C ^ 2, from above, the maximum value of C ^ 2 is 1,
That is, a (2-A) > = 1, we can get - (a ^ 2 + 2A + 1) = (a + 1) ^ 2 > = 0, we can get a = 1
Then | A-B | = | 1-B | > = 0, the range of B is 0b, B

The experiment of measuring small light bulb by voltammetry and the function of sliding rheostat
In this experiment, the function of sliding rheostat is to reduce the error of the experiment, so as to find the influence on the small lamp! It's the function of sliding rheostat!

Divide voltage and protect small light bulb

In △ ABC, B &# 178; + C &# 178; = a &# 178; + BC, and vector AC &# 8226; vector AB = 4, find s △ ABC

In this paper, we have obtained the following cosine theorem: the cosine theorem: the cosine theorem: the cosine theorem: the cosine theorem is as follows: the COSA is a = (B \35\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\) / 2 vector AC &; vector AB = 4 is equivalent to BC · cosa = 4, so BC = 8, s △ ABC = (1 / 2) BC · Sina = (1 / 2) · 8 · (radical 3) / 2 = 2 times radical 3

What is the function of sliding rheostat in measuring resistance and power by voltammetry?

In this experiment, the function of the sliding rheostat is to change the resistance of the sliding rheostat into the circuit, so as to change various physical quantities (including current and voltage) in the circuit, so as to achieve the effect of multiple measurements
The purpose of multiple measurements is to find the average of multiple measurements and make the experimental results more prepared