Step-by-step explanation:
By Cosine rule, we have
s² = t² + u² - 2(t)(u)(cosS)
=> cosS = (t² + u² - s²)/2tu
=> cosS = (58² + 27² - 50²) / (2 * 58 * 27) = 0.5086.
Therefore S = cos^-1(0.5086) = 59.4° (1d.p.)
Answer:

Step-by-step explanation:
Using the rule of exponents
⇔ 
Given
=
= 
A+B+C+D+E=540°
4X+5+7X+6X+10+5X-5+4X+10=540
26X = 520
X = 520 : 26 = 20°
E = 4X + 10 = 80 + 10 = 90 °
(b - 4z)/7 = a
b - 4z = 7a
b = 7a + 4z
Answer: b = 7a + 4z
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