# If the hypotenuse of a right triangle is 10 units and angle B is 70 degrees determine angle A and the other sides of the triangle.

### 3 Answers | Add Yours

Let's suppose that the right **angle is A = 90 degrees**. The hypotenuse is opposite side to the right angle.

That means that B+C = 70 + C = 90

C = 90 - 70

**C = 20 and B = 70**

To determine the lengths of the other cathetus, we'll apply the Pythagorean theorem and the sine function.

The sine function is a ratio between the opposite cathetus and the hypothenuse. We'll note the cathetus as x and y.

sin B = x/10

sin 70 = x/10

x = 10*sin 70

x = 10*0.93

**x = 9.4 units**

We'll apply Pythagorean theorem in a right angle triangle:

10^2 = x^2 + y^2

100 = 88.36 + y^2

y^2 = 100 - 88.36

y^2 = 11.64

**y = 3.4 units**

We'll keep only the positive value for y, since it is the length of the cathetus of the right angle triangle and it cannot be negative.

We have a right angled triangle and one of the sides given as 70 degrees. Now the second side is 180 - 90 - 70 = 20 degrees.

Also, the hypotenuse is 10. Let the other sides be a and b.

So cos 70 = a / 10 =.3420

a = .3420*10 = 3.420

cos 20 = b/ 10 = .9396

b = 0.9396*10 = 9.396

**Therefore the sides of the triangle are 10, 3.42 and 9.396. The angles of the triangle are 90, 70 and 20 degrees.**

Given the triangle ABC such that:

B = 70 degrees.

Then The other angles are:

A = 90 degrees.

C = 20 degrees.

Then the hypotenuse is BC = 10 units.

Now we will calculate the length of the legs.

==> AC = BC*cos B = 10*cos70 = 10*0.3420 = 3.42 units

==> AB = BC*cos C = 10*cos20 = 10*0.9397 = 9.367 units.

**Then the angles of the triangle are:**

**A = 90 degrees**

**B = 70 degrees.**

**C = 20 degrees.**

**The length of the sides are:**

**AB = 9.367 units.**

**BC = 10 units.**

**AC = 3.42 units.**